Image processing system

There is disclosed an image processing system for enabling efficient image formation, preparation of plural copies and easier image synthesis. For this purpose the system has a page memory in which the image information can be stored and can be synthesized with another image information which is sent directly from an image reader to an image output device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image processing system, and more 
particularly to an image processing system for image formation in response 
to image signals supplied from an image output unit such as an image 
reader. 
2. Description of the Prior Art 
There is already proposed an image processing apparatus fo image formation 
in response to the image signals by optically reading an original with an 
image sensor such as a charge-coupled device (CCD), but in such known 
apparatus an image signal generating unit is combined with an image 
forming unit whereby the original reading operation has to be repeated for 
each image formation in case plural image formations are required. Also 
the synthesis of two images requires a memory of a very large capacity and 
is therefore inefficient costwise. 
Also the image signal generating unit has to match the following image 
processing unit, and has often to be renewed or replaced in case of a 
change in the system. 
Also in case an image processing system composed of plural units is 
entirely controlled by a single unit, such controlling unit is heavily 
burdened and the control process becomes very complicated. 
SUMMARY OF THE INVENTION 
In consideration of the foregoing, an object of the present invention is to 
provide an image processing system capable of achieving efficient image 
processing. 
Another object of the present invention is to provide an image processing 
system adapted for the formation of plural images. 
Still another object of the present invention is to provide an image 
processing system capable of synthesizing plural image information with a 
simple structure. 
Still another object of the present invention is to provide an image 
processing system operable with a simplified system control. 
Still another object of the present invention is to provide an image 
processing system capable of high-speed image processing. 
The foregoing and still other objects of the present invention, and its 
effects will become apparent from the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an external view of a system embodying the present invention, 
wherein a reader 1 for reading an original image by means of an image 
sensor such as a charge-coupled device (CCD) is connected, through signal 
lines, to an image information memory, called a retention memory unit 
(RMU) 2, which stores and releases the image information supplied from 
said reader 1 in the form of electrical signals. Similar signal lines from 
the retention memory unit 2 are connected to a multi-input-multi-output 
unit (MIMOU) 3. For effective use of said retention memroy unit, there may 
be applied known signal compression or expansion process to the image 
information. The multi-input-multi-output unit 3 is further connected, 
through signal lines, to printers 4, 5 for image recording on recording 
material such as paper sheets. Although two printers are connected to the 
multi-input-multi-output unit, there may be employed more or less 
printers. In the present embodiment, there may be employed, as will be 
explained later, four readers and eight printers at maximum. 
Though the retention memory unit 2 is connected between the reader 1 and 
the multi-input-multi-output unit 3 in the structure shown in FIG. 1, it 
may be connected at any position between the reader and the printer, for 
example between the multi-input-multi-output unit 3 and the printer 4 or 
5. As will be explained later, the above-mentioned units mutually exchange 
a vertical synchronization signal VSYNC for image signals, a video enable 
signal VE for indicating a line of the image, image signals VA and VB, an 
image synchronization signal VCLK and a horizontal synchronization signal 
BD, as well as common serial control signals for the transmission of said 
image signals. Consequently the units can be combined arbitrarily if same 
input/output devices are emplyed in these units for signal exchange. The 
unit formation of various parts of the image processing system and the 
mutual connection through signal lines of common structure allows easy 
assembling and disassembling of various units with a reduced cost. Also 
such structure permits expansion of the system for example through 
connection of plural multi-input-multi-output units. 
Now reference is made to FIGS. 2 to 6 for explaining the detailed structure 
of the reader 1, retention memory unit 2, multi-input-multi-output unit 3 
and printers 4, 5. 
FIGS. 2(a) and 2(b) show the internal structure of the reader 1. In the 
present embodiment, for achieving high-speed image reading with a high 
resolving power, the original image is divided into two areas and is read 
with two CCD's and the obtained signals are jointed to obtain image 
signals of a line. 
At first reference is made to FIG. 2(a). 
Optical lenses 10, 11 focus the image of an original ORG, placed on an 
unrepresented support, onto CCD's 12, 13. The original is scanned with an 
unrepresented optical system by means of a known technology which will not 
be explained in detail. 
The CCD's 12, 13 convert the density of the original image into electrical 
signals, which are amplified in amplifying circuits 14, 15 and converted 
by analog-to-digital (A/D) converters 16, 17 into multi-bit digital 
signals representing the image density for each pixel. 
Said digital signals are subjected, in shading correction circuits 18, 19, 
to the elimination of shading resulting from uneven intensity of the light 
source, uneven luminance distribution of the optical system, uneven 
sensitivity distribution of CCD's etc., and are supplied to ternary 
encoding circuits 20, 21 for conversion into ternary digital image signals 
VD1-A, VD1-B, VD2-A and VD2-B for achieving satisfactory reproduction of 
intermediate tones. 
The ternary encoding is achieved by parallel binary encodings with 
different binary encoding levels. Selectors 22, 23 select either one of 
two ternary encoding methods, namely a method of employing fixed binary 
encoding levels given by a latch circuit 26 and a so-called dither method 
of employing binary encoding levels periodically modified in a determined 
matrix size by dither read-only memories 24, 25. Said dither method is 
widely employed for example in the facsimile for pseudo tonal reproduction 
with binary signals. As will be explained later, output of binary image 
signals may sometimes be required instead of ternary image signals. In 
such case, a suitable binary encoding threshold value is supplied from the 
latch circuit 26 or from the dither ROM's 24, 25. 
In the present embodiment it is rendered possible to obtain an optimum 
image reproduction by adopting the method with determined binary encoding 
levels for the originals containing characters, and the dither method for 
the originals requiring tonal reproduction such as photographs. It is also 
possible to adopt a method in which two similar binary encoding levels are 
given by the latch circuit 26. 
The dither ROM's 24, 25 provide, in successive manner, the dither patterns 
stored at addresses given by a counter 27 for counting the number of lines 
in the sub-scanning direction along the length of the original and 
counters 28, 29 for counting the number of pixels in the main scanning 
direction taken across the original. In order to prevent distortion in the 
dither pattern at the jointing of the electrical signals obtained from the 
CCD's 12, 13, a latch circuit 30 is connected to the counter 29 for 
providing preset data of a optimum count. 
Said latch circuit 30 and other latches shown in FIG. 2 are connected, 
through unrepresented signal lines, to a CPU bus of a CPU 38, for data 
latching by the CPU 38. The CPU 38 functions according to a control 
program stored in a ROM 39 to control the entire reader through a RAM 40, 
an I/O port 41, a timer circuit 42, a serial circuti 43 and a key display 
driving circuit 44. 
Also the CPU 38 performs control for requlation and confirmation of 
functions according to the values selected by a dip switch unit 46. 
The key display driving circuit 44 is provided for scanning the key matrix 
of an operation unit 45 and driving a display unit composed for example of 
light-emitting diodes (LED). The serial circuit 43 is provided for 
supplying control instructions to and receiving information from the 
printer, multi-input-multi-output unit and retention memory unit. 
An oscillator circuit 32 provide timing signals to a CCD driving circuits 
31 for driving the CCD's 12, 13 and other circuits relating to the image 
signals. Said signals are counted by a counter 33, of which count is 
supplied to a decoder 34 for defining various timings. 
The decoder 34 generates and supplies an internal synchronization signal HS 
for each line in the sub-scanning direction to a selector 35, which also 
receives a similar synchronization signal BD supplied, as will be 
explained later, from the printer when it is connected. The CP 38 
automatically selects, according to the procedure shown in the flow chart 
of FIG. 12, the signal BD when the printer is directly connected to the 
reader, or the signal HS when the multi-input-multi-output unit or the 
retention memory unit is connected to the reader. The signal thus selected 
is used as a synchronization signal HSBD for the sub-scanning direction. 
Said signal HSBD is also supplied to the counter 33 as a count resetting 
signal. 
The counter 33 releases original clock signals used for storing the image 
signals VD1, VD2 into memories 60-63 to be explained later, and said 
original clock signals are converted into memory write-in signals WCLK by 
a rate multiplier 36, which divides the frequency of the entered clock 
signals by the value of a control signal supplied from outside, in the 
present embodiment from a latch circuit 37. Said rate multiplier is used 
in the present embodiment for modifying the image magnification in the 
main scanning direction. 
Now reference is made to FIG. 2(b). 
Latch circuits 50, 51, 52 provide preset data respective for a write 
counter 53 and read counters 54, 55. The write counter 53 generates memory 
addresses, from the signal WCLK supplied from the rate multiplier 36 shown 
in FIG. 2(a), for writing the signals VD1-A, VD1-B, VD2-A and VD2-B in the 
memories 60-63. The read counters 54, 55 generate memory addresses, from a 
signal RCLK to be explained later, for reading the signals VDl, VD2 from 
the memories 60-63. 
The memory address signals released from the write counter 53 and the read 
counters 54, 55 are selected by selectors 56-59 and supplied to the 
memories 60-63. 
The memories are divided into sets 60, 61 and 62, 63, one of which performs 
write-in operation while the other performs read-out operation, thus 
achieving the conversion of the signal rate. 
Each set of memories alternately performs the write-in and read-out 
operations, respectively in response to the signal from the write counter 
53 and the signals from the read counters 54, 55, selectively supplied 
from the selectors 56-59. The repetition of said write-in and read-out 
operations is controlled by the aforementioned signal HSBD. 
The signals VD1-A, VD1-B, VD2-A and VD2-B read from the memoreis 60-63 are 
supplied to a selector 70 for synthesizing the image signal of a line for 
each of the ternary levels, then subjected to image editing such as image 
inversion or trimming in an image processing circuit 71, and supplied as 
two separate binary or ternary image signals VDA, VDB to the printer, 
retention memory unit or multi-input-multi-output unit. 
An oscillator circuit 66 generates an oscillation signal used as the 
reference timing for the signal read-out operation. Said oscillation 
signal is supplied to the printer etc. as a video clock signal VCLK which 
is a synchronization signal common for two separate image signals VDA, 
VDB. A control circuit 67 for the signal write-in control in response to 
the signal HSBD from the selector 35 controls the function of a left 
margin counter 68 and a bit counter 69 at determined timings to be 
explained later. 
A rate multiplier 64 and a latch circuit 65 generate a read-out clock 
signal RCLK in the same manner as the aforementioned rate multiplier 36 
and latch circuit 37. Also the control circuit 67 supplies a video enable 
signal VE, to be explained later in relation to FIG. 7, to the printer 
etc. 
The separate outputs through plural signal lines of the multi-level 
information obtained by original reading one to use the video clock 
signals of a lower frequency compared to the case of output of synthesized 
information, thus enabling one dispense with the use of high-performance 
components in the input and output circuits and of high-performance 
transmission channels capable of responding to high frequencies and to 
reduce the circuit cost and to improve the performance such as noise 
resistance. 
Now reference is made to FIG. 3 for explaining the control circuit for the 
retention memory unit 2, which is composed of a memory section and a 
control section. A microcomputer 75 in the control unit is connected, 
through a CPU bus, to a ROM 76, a RAM 77, an I/O port 78, a timer circuit 
79 and a serial communication circuit 80, which perform same functions as 
those in the reader unit. The I/O port 78 is connected to the selector 
etc. in the memory 
section. The serial circuit 80 is rendered connectable in parallel manner 
to the reader unit and the printer unit. A selector 301 selects either a 
signal HS from an HS generator 300 in case the retention memory unit and 
the printer are connected through the multi-input-multi-output unit, or a 
signal BD from the printer in case the retention memory unit is connected 
directly with the printer. 
The memory section is composed of a memory A 85 and a memory B 86, each of 
which is composed for example of a dynamic RAM with a capacity for storing 
image information of an original of A3 size. They may also be composed of 
other memory components such as optomagnetic disks. Selectors 97, 98 are 
provided in the input lines of said memories for storing the ternary image 
signal of two series VDA, VDB respectively in the corresponding memories. 
Also the selectors 97, 98 can store the image signal generated as binary 
signal into either one or both of the memories A and B. The image signal 
selected by the selector 97 is written into a shift register lA (82) in 
synchronization with the video clock signal VCLK, and is then stored into 
the memory A (85) in synchronization with the address signal supplied from 
an address generator 83. Similarly the image selected by the selector 98 
is stored in the memory B (86) through a shift register lB (84). The 
storage of two image signals is thus controlled by the common video clock 
signal VCLK. The address generator 83 for memory addressing controls the 
addressing in the memories A, B in synchronization with a video clock 
signal VCKS and a video enable signal VES. 
A selector 81 receives the clock signal VCLK supplied from the outside, for 
example from the reader, together with the image signal and an internal 
lock signal ICLK generated in an internal clock generator 91, and, in the 
signal write-in operation into the memory, selects the former to generate 
the video clock signal VCKS for supply to the address generator 83. Also a 
selector 88 receives the video enable signal VE supplied from the outside, 
for example from the reader, together with the image signal and an 
internal signal IVE generated in an internal video enable signal 
generator, and selects the former as the video enable signal VES to be 
supplied to the address generator 83. Said address generator 83 is used 
also for the image signal read-out from the memories A, B. The start 
timing for the signal write-in or read-out of the memories A, B is given 
by the CPU 75 through the I/O port 78. 
The image signals in the memories A, B (85, 86) ar read in response to the 
address signals from the address generator 83, stored in shift registers 
2A, 2B (89, 90) and then released as serial data in synchronization with 
the common video clock signal ICLK generated in the internal clock 
generator 91. In this operation the selector 81 selects the internal clock 
signal ICLK as the video clock VCKS. The video enable signal generator 87 
is similar to the HSBD generator in the reader unit and generates the 
clock signal IVE in a timing shown in FIG. 7. 
Two separate serial image signals released simultaneously from the memories 
A, B through the shift registers 2A, 2B are selected by selectors 92, 93 
for supply either to an image signal line A or B. OR circuits 94, 95 add 
the output of the selector 92 I5 or 93 and an image signal from a bypass 
gate 99 and releases the image information containing two synthesized 
images. There are also provided gate circuits 72, 73 for obtaining 
synthesized information from the outputs of both memories A, B and the 
bypassed image signal, thus allowing the gate circuits to synthesize the 
three images. A selector 96 is provided to select, for supply to the 
succeeding unit, either the video clock signal VCLK supplied from the 
outside or the internal video clock signal ICLK generated by the internal 
clock generator 91 according to the operation mode. 
As explained in the foregoing, the retention memory unit is provided with 
memories of a number corresponding to the number of signal lines for 
multilevel image information, and enables signal storge into each memory 
by a selector provided for each memory. Consequently image information 
solely composed of white and black and not requiring ternary reproduction, 
such as a business format, can be stored in either one memory, so that the 
memory for one page of ternary image signal may be used for two pages of 
binary image signal. 
Also the presence of plural image memories for respective storage of two 
separate image signals constituting ternary information, with the 
possibility of independent output or of output to either of plural signal 
lines through the selector provided in each memory, expands the ability of 
image reproduction, for example obtaining a synthesized image in which the 
image of an original is reproduced denser while the image stored in the 
memory is reproduced paler by adding the image signal of the original 
obtained through the bypass gate 99 to the image signal of a ternary 
signal line alone representing a low image density. 
It is also possible, in a system for transmitting an image in the form of 
multi-level image information through plural lines, to control plural 
signal channels by a common synchronization signal, thereby simplifying 
the input/output circuits for the image information and reducing the 
number of signal lines, thus achieving a lower cost. 
Furthermore, the retention memory unit is provided with memories of a 
number corresponding to that of image signal lines, said memories being 
constructed to perform signal write-in and read-out by means of a common 
address generator. It is therefore possible to control plural memories 
with a simple circuit. Furthermore, a higher speed in the image 
reproduction and an improved image control function are achieved since the 
retention memory unit is constructed to synthesize the image signal from 
the reader unit and the image information already stored in said memory 
unit when said image signals are released. 
Furthermore the retention memory unit receives the image signal in the same 
manner as the printer unit at the image write-in operation and releases 
the image signal in the same manner as the reader unit at the image 
read-out operation, whereby the reader unit can be controlled without 
consideration on the difference between the printer and the retention 
memory unit, and the printer or the multi-input-multi-output unit can be 
operated without consideration on the difference between the reader unit 
and the retention memory unit. These facts lead to easier development of 
these units, freer connection between them and easier system composition. 
FIG. 4 shows the structure of the multi-input-multi-output unit (MIMOU) 
100, together with three readers 101-103, eight printers 111-118 and 
another reader 104 connected through a retention memory unit 148. The 
position of connection of said retention memory unit can be changed 
arbitrarily. 
The MIMOU 100 is composed of a multi-input-multi-output controller (MIMOC) 
120, synchronous memory boards (SBD) 121-128 respectively corresponding to 
the printers 111-118, and an operation section 147. 
The MIMOC connected to the readers 101-103 and the retention memory unit 
148 and is provided with serial circuits 131-134 to be respectively 
connected to the serial circuits 43 of the readers and of the retention 
memory unit, and a serial circuit 135 to be connected to the printers 
112-118 through the SBD's. Said circuits are controlled by a CPU 140, 
which functions according to a control program stored in a ROM 141 
connected to a CPU bus and controls the entire MIMOU 100 through a RAM 
142, an I/O port 143, an interruption controller 144, a timer circuit 145 
and a key display driving circuit 146 connected to the CPU bus. The 
retention memory unit can be connected to any terminal of the MIMOU 100, 
since all the units I have a common connection as explained already in the 
foregoing. 
The MIMOC 120 is provided with a control bus CB and an image bus IB 
connected to the SBD's 121-128. 
The image bus IB is a signal bus for transmitting the image signal and the 
control signal therefor supplied from the readers 101-103 and the 
retention memory unit 148. 
The control bus CB is a signal bus for the serial signals generated by a 
serial circuit 135 for communication between the printers 111-118 and the 
MIMOU 100, and an SBD control signal of an I/O port 143. 
In the present embodiment, the copy start instruction is given by the 
reader, and the MIMOU 100 functions as a slave to the reader. Thus, in 
order to receive the serial signals from the reader or from the retention 
memory unit at any time, the MIMOU 100 is provided with a serial circuit 
for each image signal releasing unit, and all the serial signals are 
handled by a CPU 140. On the other hand, the MIMOU 100 functions as a 
master to all the printers and performs the serial signal communication in 
successive manner with different printers through a serial circuit 135. 
The operation section 147 scans a key matrix and drives a display unit 
through the key/display driving circuit 146. 
The SBD 121-128 are used for synchronizing the function of the printers 
with the image signals supplied from the readers or from the retention 
memory unit, as will be explained later in relation to FIG. 5. 
FIG. 5 shows an example of the circuit structure of the SBD 121-128. 
In FIG. 5, a selector 150 selects a reader control signal designated by the 
CPU 140, from image control signals supplied from plural readers and the 
retention memory unit. The selected control signal is supplied to a write 
counter 151 and a VE counter 152 for generating a address signal for 
storing the image signal into memories 171-178 and a selection signal for 
signal storage into the memories. 
A selector 182 selects the image signals VDA, VDB supplied from the readers 
and the retention memory unit, and the selected image signals are supplied 
to the memories 171-178 in parallel manner and stored in the memories 
selected by selectors 161-168. 
The write counter 151 generates address signals for the storage of the 
image signals VDA, VDB into the memories 171-178 and supplies said address 
signals to the selectors 161-168. 
The VE counter 152 counts the control signal VE indicating a line of the 
image and supplies the count to a decoder 153 for generating a selection 
signal for selecting one of the memories 171-178 for signal write-in nad 
supplyuing said selection signal to the selectors 161-168. 
These circuits are initializing by a control signal VSYNC indicating the 
start of an image supplied from a connected reader. The data write-in is 
conducted in cyclic manner, in the order of 171, 172, 173, . . . , 177, 
178, 171, . . . 
On the other hand, the signal read-out from the memories 171-178 is 
initiated when the image signal is stored in a half of the memories, 
namely when the image signal is stored in the memory 174 in the present 
embodiment. A control signal for starting said signal read-out is 
generated in the decoder 153 which selects a memory for storing the image 
signal, and is supplied to a BD control circuit 154. 
The BD control circuit 154, after being initialized by said signal VSYNC, 
prohibits the output. as a signal BD', of a signal BD supplied from a 
connected printer until the reception of a control signal for initiating 
the signal read-out from the decoder 153. When said prohibition is 
cancelled, the signal BD' activates a control circuit 158, thus effecting 
the signal read-out from the memories in cyclic manner, as in the signal 
write-in operation, in the order 171, 172, 173, . . . , 177, 178, 171, . . 
. 
An oscillator circuit 155, a control circuit 158, a left margin counter 156 
and a bit counter 157 correspond to and have substantially the same the 
functions as the oscillator circuit 66, control circuit 67, left-margin 
counter 68 and bit counter 69 of the reader shown in FIG. 2. A difference 
lies in the fact that a signal VE' similar to the signal VE is generated 
by the control circuit 158 and supplied to a VE' counter 180. 
The VE' counter 180 counts the VE' signal, and the obtained count is 
supplied to a decoder 181 for generating a selection signal for 
determining a memory for signal read-out. The selection signal is supplied 
to the selectors 161-168. 
The selectors 161-168 control the signal write-in to or the signal read-out 
from the memories 171-178 in response to the signal from the write counter 
151 and decoder 153, or from the bit counter 157 and decorder 181. 
A selector 187 selects the image signal from a selected memory, among the 
image signals read from the memories 171-178, and sends thus selected 
image signal VDA, VDB to a printer. 
The control bus CB supplies signals to a latch circuit 183, an interface 
circuit 184 and a control circuit 185. 
The latch circuit 183 latches a select control signal to the selectors 150, 
182. Said latching is effected when the control circuit 185 identifies 
that the number of SBD designated by the control bus CB coincides with a 
value set by a dip switch 186. The control between the MIMOC 120 and the 
SBD's is effected by a value selected by the dip switch 186 in this 
manner. 
As explained before, various processing apparatus are constructed as 
separate units, and the retention memory unit and the MIMOU are connected 
between the readers and the printers. Since a common interface is employed 
through various units, the operation of the system is possible regardless 
whether the retention memory unit is connected or not and further 
regardless of the order of connection of the retention memory unit and the 
MIMOU. Thus the system structure is flexible and can be adjusted to the 
requirement of the operator. 
FIG. 6 shows the structure of the printer, which can be connected directly 
with the reader of indirectly through the retention memory unit and the 
MIMOU 100. 
The serial signal from the MIMOU 100, readers or retention memory unit is 
supplied to a serial circuit 201 and processed in a CPU 200, which 
function according to a control program stored in a ROM 203 and controls 
the entire printer through a RAM 204, a timer circuit 202 and an I/O port 
205. 
An input interface 207 performs the input processing for sensor signals 
etc. for example for sheet detection in the printer. A driving circuit 208 
drives unrepresented motor, high-voltage transformer etc. A display 
circuit 206 is used for displaying printer status such as absence of 
sheets, sheet jamming etc. 
The image signals VDA, VDB supplied from the MIMOU 100 or the reader are 
synthesized into a ternary image signal VD in a synthesizing circuit 217, 
then supplied to a laser drive 209 and converted into a laser beam 
corresponding to the signal VD in a semiconductor laser 210. Said laser 
beam is focused by a collimating lens 211 and performs a scanning motion, 
by means of a polygonal mirror 212, in a direction substantially parallel 
to the rotary axis of a photosensitive drum 214 rotating at a determined 
speed. The scanning laser beam is subjected to the correction of light 
intensity by an f-.theta. lens 213 to form a latent image on the 
photosensitive drum 214 corresponding to the signal VD. 
The image formation in the printer is conducted in so-called electrostatic 
recording process, in which a latent image is formed by selectively 
eliminating, by means of the laser beam, the electrostatic charge given in 
advance to the photosensitive drum 214 and is then rendered visible by 
developer, and the obtained visible image is transferred onto a print 
sheet and fixed thereon. The electrostatic recording process will not be 
explained in further detail since it is already well known. 
The laser beam performing the scanning motion by the polygonal mirror 212 
enters an optical fiber before irradiating the photosensitive drum 214, 
whereby a photosensor 216 generates an electrical signal BD. As will be 
understood from FIG. 7, the reader, retention memory unit or MIMOU 100 
releases the video enable signal VE after the lapse of a period, from the 
generation of said signal BD, corresponding to the time required for the 
laser beam to reach the photosensitive drum 214, in order to form the 
latent image in an appropriate position on the photosensitive drum 214. 
FIG. 7 is a timing chart showing the timing of said signal VE in more 
detailed manner. 
FIG. 7 shows a case where the printer is connected to a reader, but the 
situation is same even when it is connected with the MIMOU or the 
retention memory unit. 
As shown in FIG. 7, the left margin counter 68 starts counting at the 
generation of the signal BD or HSBD, and, upon completion of the counting 
operation corresponding to the above-mentioned period, the bit counter 69 
is activated to start the read-out of the signal VD from the memories 60, 
61 or memories 62, 63. The bit counter 69 terminates the function thereof 
after the output of the signal VD over an area for latent image formation 
on the photosensitive drum 214 and prepares for the entry of a succeeding 
signal HSBD responding to the succeeding signal BD. 
The signal VE indicates the period of function of the bit counter 69, 
namely the period of input or output of the image signal of a line, and is 
used for controlling the function of the MIMOU, VE counter 152 and write 
counter 151. The signal VE' generated in 
the control circuit 158 in the MIMOU has a similar purpose. 
FIG. 8 is a timing chart of the image signals in the synthesizing circuit 
217 shown in FIG. 6. The image signals VDA, VDB are supplied in 
synchronization 
with the video clock signal VCLK. The synthesizing circuit 217 alternately 
selects said signals VDA, VDB with a frequency equal to the double of that 
of said video clock signal to obtain an image signal VDO synthesized from 
two image signals. 
FIG. 9 shows an operation panel provided in the reader connected to the 
present system. Said operation panel is composed of a standard operation 
section 252, a preset operation section 251, and a special operation 
section 250 including a liquid display device 256 and software keys 257. 
The standard operation section 252 is provided with numeral keys 254 for 
setting the copy number, a preset copy number display device 252, a copy 
start key 253 etc. and can be manipulated in the same manner as in the 
ordinary copier. 
The special operation section 250 for creating arbitrary code modes is 
provided with a liquid crystal display device 256 for displaying labels, 
copy modes, data and various messages, and six software keys 257, wherein 
a copy mode can be created by depressing a software key positioned under a 
display which the operator wishes to adopt. 
For example a sheet size can be selected among plural sheet sizes displayed 
in succession on the display device, by depressing a software key 
positioned under said desired sheet size. Also the liquid crystal display 
device 256 can display information which cannot be displayed in the 
standard operation section, for example the number of printers employed in 
a copying operation with plural printers. 
The preset operation section 251 is used for registering a copy mode or 
condition selected by the standard operation section 252 or by the special 
operation section 250. More specifically, a frequently used copying mode 
is registered in a RAM 40 and is restored by a key, without the use of the 
special operation section 250. 
The various units can be connected in four ways, namely a connection of a 
reader with one or plural printers through a retention memory unit and a 
MIMOU, a connection of a reader, a retention memory unit and a printer, a 
connection of a reader, a MIMOU and one or plural printers, and a 
connection of a reader and a printer. In the present system arbitrary 
connection is possible because of a common input/output interface in the 
various units. The connection status is identified by an application 
status software to be explained later. The readers and the retention 
memory unit are connected to the MIMOU through the serial circuits having 
respective numbers as explained before, so that the MIMOU handles said 
numbers as representative of the readers connected thereto or the reader 
connected through the retention memory unit. Also the MIMOU is connected 
with the printers and the retention memory unit through the synchronous 
memory boards, so that the MIMOU handles the value of the dip switch 186 
on each synchronous memory board as a number representative of each 
printer. 
In case the readers are connected to the MIMOU either directly or 
indirectly through the retention memory unit and further connected to the 
printers, there may be selected a single mode or a multiple mode in the 
readers. 
In the single mode, each reader is connected by the MIMOU to a printer of a 
number same as that allotted to the reader, in which the reader receives, 
through the MIMOU, the station status of a single printer. 
In the multiple mode, a reader can be connected through the MIMOU to 
unspecified plural printers which can be selected in the operation section 
of the reader. In the multiple mode the selection of the printers may be 
achieved by the MIMOU, in which case the MIMOU selects a necessary number 
of printers from those available at that time, depending on the preset 
copy number. In the multiple mode, the operation status of the printers 
are assembled by the MIMOU in an appropriate form and supplied to the 
reader. 
There will now be explained the process of communication in a system 
composed through the MIMOU and the retention memory unit, as the control 
for a connection of a reader and a printer is same as that of the single 
mode utilizing the MIMOU. The difference between the single mode and the 
multiple mode will be explained wherever applicable in the following 
explanation. 
The operation utilizing the retention memory unit shown in FIG. 3 includes 
four modes, i.e. a retention mode in which the image signal from the 
reader is stored in the retention memory unit and is simultaneously 
supplied to the printer for image reproduction, whereby a first copy is 
obtained by the image signal from the reader while second and ensuing 
copies are reproduced from the output signal from the retention memory 
unit, an overlay mode for synthesizing image information stored in advance 
with an image signal supplied from the reader for image reproduction in 
the printer, a store mode for storing the image signal from the reader 
into the retention memory unit, and a monitor mode for image reproduction 
in the printer by the image signal already stored in the retention memory 
unit. These modes can be selected by the reader and the retention memory 
unit (RMU) functions in any mode in response to the instruction supplied 
from the reader. 
Now reference is made to FIG. 10 for explaining certain examples of setting 
the mode of the retention memory unit through the special operation 
section 250 of the reader. In FIG. 10 there are shown the liquid crystal 
display device 256 and six software key 256 (SK1-SK6). The liquid crystal 
display 256 performs displays corresponding to the keys SK1-SK6. 
When the power supply is turned on, the liquid crystal display 256 
displays, as shown in FIG. 10 (1), a message "ETC" (et cetra) in a 
position corresponding to the key SK6. The displays corresponding to the 
keys SK1-SK5 change in cyclic manner by the repeated depressions of the 
key SK6, thus enabling selection or change of the input mode according to 
the system structure. 
In response to the signals from the printers, the reader understands the 
units connected in the system and allows the user to select the input mode 
suitable for the system structure. 
When the retention memory unit (RMU) is connected in the system, there is 
displayed a state for selecting an RMU input mode as shown in FIG. 10(2) 
upon repeated depressions of the key SK6. In said state, the RMU mode is 
selected by depressing the key SK2 corresponding to a display "RMU?". If 
the RMU mode is not desired, the key SK6 corresponding to the display 
"ETC" is depressed whereby the display changes to a succeeding input mode. 
Also the display shown in FIG. 10(2) is not given if the RMU is not 
connected. 
Upon depression of the key SK2 in the state shown in FIG. 10(2), the RMU 
mode is selected and the display changes as shown in FIG. 10(3). In this 
state the keys SK1-SK4 respectively correspond to displays "RTC?", "OVL?", 
"STR?" and "MNT?", respectively indicating the retention mode (high-speed 
retention utilizing memory), overlay mode (overlay of the stored image and 
an original), stored mode (storage of an original into the memory), and 
monitor mode (image reading from the memory). Also in response to the 
depression of the key SK6 corresponding to a display "BACK", the display 
returns to the state shown in FIG. 10(2) whereby the selection of the RMU 
mode is cancelled and the input mode for selecting the RMU mode is 
restored. 
The display state shown in FIG. 10(3) allows one to select one of four RMU 
modes. For example, the retention mode is selected by the depression of 
the key SK1 corresponding to the display "RTC?", whereupon the display 
changes to "RTC!!". The mark "?" indicates that the corresponding mode is 
not yet selected, and the mark "!!38 indicates that said mode has been 
selected by the depression of the corresponding SK key. 
After the retention mode is selected, the operator sets the copy number 
through the numeral keys 254 and depresses the start key 253 as in the 
ordinary copier to initiate the high-speed retention operation utilizing 
the retention memory unit, namely the image formations of a desired number 
by one original image reading and plural signal read-outs from the memory. 
In this mode the selectors in the retention memory unit are activated in 
storing two separate ternary image signals VDA, VDB, obtained from the 
reader, into the corresponding memories A, B. 
The overlay mode is selected by the depression of the key SK2 corresponding 
to the display "OVL?" shown in FIG. 10(3). Upon said selection the display 
changes to a state shown in FIG. 10(5), and, after a determined time, to a 
state shown in FIG. 10(6) for awaiting the key entry. 
In this state the operator selects the image(s) stored in the memory A 
and/or B for overlay with the image of the original. There are given 
displays "MEMA", "MEMB" "MEAB" and "MA+B" respectively corresponding to 
the keys SK1-SK4 and representing the overlays with the memory A, with the 
memory B, with the memories A, B and with the memories A+B as will be 
explained later more detailedly. The operator actuates one of the keys 
SK1-SK4 for selecting the memory or memories desired for image overlay, 
then sets the copy number by the numeral keys 254 and depresses the start 
key 253, whereby the overlay of the image of an original under reading 
operation and of the image already stored in the retention memory unit is 
repeated for a desired number of times. 
Also the storage mode is selected by the depression of the key SK3, in the 
RMU input mode, corresponding to the message "STR?", whereupon the display 
changes, through a state shown in FIG. 10(7), to a state shown in FIG. 
10(8) awaiting the key entry. In this state the operator selects the 
memory or memories of the retention memory unit for storing the image 
signal read in the reader, by depressing one of the keys SK1-SK3 
respectively corresponding to the memory A, memory B or memories A and B. 
The reader releases the image in the state of binary signals in case 
either one of the memories A and B is selected, or in the state of ternary 
signals in case both memories A and B are selected for storage. Upon 
depression of the start key 253 after the memory selection, the original 
reading operation and the information storage are initiated without the 
image printing, and these operations are conducted as a preparation for 
the overlay mode or the monitor mode. 
Similarly the monitor mode is selected by the depression of the key SK4 
corresponding to the display "MNT?" in the RMU input mode, whereupon the 
display changes through a state shown in FIG. 10(9) to a state shown in 
FIG. 10(10), thus awaiting the key entry for selecting memory or memories 
of the retention memory unit for reading the image signals stored therein. 
The keys SK1-SK3 in this state respectively correspond to the memory A, 
memory B and memories A and B. After the depression of a key SK 
corresponding to the memory or memories for signal read-out, the operator 
sets the cop number by the numeral keys 254 and depresses the start key 
253 to execute the monitor mode, in which the image information read from 
the selected memory or memories is printed over a desired number of times. 
As explained in the foregoing, the presence of the retention memory unit 
enables the reader to select one of four modes, i.e. the retention mode, 
overlay mode, sotrage mode and monitor mode. 
Also the presence of the retention memory unit is displayed on the 
operation section of the reader so that all the units connected to the 
system can be easily identified in the reader. Consequently the operator 
can easily cope with the expansion or reduction of the system, and an 
improvement in the operability is provided by the possibility of selecting 
various mode through the retention memory unit. 
The aforementioned multiple mode can be selected, in a similar manner as 
the above-described operation of the retention memory unit, by actuating 
the software keys corresponding to the printer numbers displayed on the 
special operation section 250, but this procedure will not be explained 
further as it was already disclosed in the Japanese Patent Application No. 
63851/1983 of the present applicant. 
Now reference is made to Tab. 14 for explaining the function of the reader, 
multi-input-multi-output unit and reader, and the communication 
therebetween in the image forming or copying operation of the present 
system. 
In Tab. 14 (A) indicates the operation at and function of the reader, (B) 
the communication between the reader and the retention memory unit, (C) 
the function of the retention memory unit, (D) the communication between 
the retention memory unit and the MIMOU, (E) the function of the MIMOU, 
(F) the communication in the MIMOU, and (G) the printer function. In the 
presentembodiment, the information exchange between the units (between 
reader and retention memory unit, between retention memory unit and MIMOU 
or between MIMOU and printer) is principally conducted by serial signal 
communication, except as to the image information. 
In these serial communications, the master function is played by tne reader 
in the communication between the reader and the retention memory unit, by 
the retention memory unit in the communication between said unit and the 
MIMOU, or by the MIMOU in the communication between the MIMOU and the 
printer. 
The master unit detects whether the slave unit is in a state capable of 
receiving serial communication, by means of a power supply signal or a 
receiption ready signal of the opponent unit, and transmits various 
commands in serial codes if the opponent unit can receive serial 
communication. The receiving unit receives said command, checks parity 
error etc. thereof and, if said command is effective, sends back a 
corresponding information. However, the retention memory unit may adopt 
another communicating method as will be explained later. Otherwise, if 
said command requires a certain function, the receiving unit perfomrs the 
corresponding function. 
The communication is conducted in a one-to-one process, in which the master 
unit releases a command code and the receiving unit returns a status code 
corresponding to said command code. 
FIG. 11 shows the basic flow of the communication of the retention memory 
unit. The communication between the reader and other units is conducted by 
the exchange of command and status of 8 bits each. The command is supplied 
from a unit at the reader side to another unit at the printer side, 
including MIMOU, and a status is returned from a unit at the printer side 
to another unit at the reader side. A command is always responded by a 
status, and the status never precedes the command. 
At first the retention memory unit (RMU) receives a cqmmand from the reader 
(S101), and identifies whether said command is data for instructing the 
RMU to be explained in relation to Tab. 13 (S102). If so, the RMU starts 
the function thereof (S103) and returns an overall status shown in Tab. 3 
(S104). In this state the command is not given to the units at the printer 
side, including MIMOU. 
If the received command is not an RMU instructing command, the RMU 
identifies whether said command need be transmitted to the printer side 
(S105) and, if not, returns the overall status to the reader side (S104). 
On the other hand, if such transmission is necessary, the RMU sends a same 
command to the printer side (S106). 
Upon reception of a command from the RMU, the unit at the printer side 
returns a status corresponding to said command within a determined period. 
Upon receiption of said status from the printer side (S107), the RMU 
identifies whether said status is an application status shown in Tab. 9 
(S108), and, if not, transmits said status to the reader side (S110). If 
it is an application status, the RMU has to attach thereto an information 
whether the RMU is connected to the system. It thus converts said status 
into a state indicating the connection of RMU (S109) and sends the status 
to the printer side (S110). 
In this manner the RMU repeats the cycle, in response to a command from the 
reader side, of transmitting said command to the printer side or returning 
an overall status to the reader side, and, in response to a status 
returned from the printer side, the cycle of sending said status to the 
reader side with or without modification in the status. 
The above-described communication process, in which the information of each 
unit is sent in the form of a code and the memory unit only accepts the 
necessary information and merely transmits other information, allows 
reduction of the time required for each information communication. Also 
the communication protocol can be simplified as the communication is 
monitored only by the unit at the reader side. 
In the following there will be given a detailed explanation on the function 
and communication of each unit shown in Tab. 14. 
Tab. 1 shows the status requesting commands by which the reader requests 
the information of the printer, and which are sent to the units at the 
reader side through the retention memory unit. In response to said status 
requesting command, the MIMOU or the printer returns, to the reader, a 
corresponding status signal as shown in Tabs. 2-11. Tab. 2 shows a command 
error status signal which is returned when the received command is 
incorrect, and in which a bit 6 is set in case of a parity error. 
Tab. 3 shows a status signal indicating, in the single mode, the status of 
a corresponding printer, or, in the multiple mode, the overall status of 
the available printers and the printers in use. A print request bit 6, 
functioning as the sheet feed enable signal, is set when all the printers 
in use become capable of sheet feeding. A sheet feeding bit 5 is set when 
the sheet feeding is proceeding in any of the printers in use. Bits 4, 3, 
2, 1 respectively indicating a misprint, a waiting process (fixing station 
in heating), a shut-off (shut-off or power economization), and a call 
error (an operation call error or a serviceman call error), are set when 
the corresponding situation occurs in all the printers in use. 
Tabs. 4 and 5 show status signals respectively for operator call errors and 
for serviceman call errors, in which the various bits correspond to the 
errors in the driving or process stations and are set in response to the 
occurence of such errors. 
Tab. 6 shows a status signal indicating the number of sheet refeeding, 
required as the result of sheet jamming or misprint. 
Tabs. 7 and 8 are status signals indicating the sheet size in the single 
mode. 
Tab. 9 shows a status signal, called application status, in which the bits 
2 and 1 respectively indicate the presence of doubly connected unit and 
the connection of the retention memory unit. The bit 2 is reset when the 
printer is directly connected to the reader, and the bit 1 is set when the 
retention memory unit is connected. 
Tab. 10 shows a status signal indicating the status of a printer designated 
by the printer information requesting command. A printer ready bit 6 
indicates that the corresponding printer is in a state ready for printing, 
and a my printer bit 5 indicates that the printer is of a number same as 
that of the reader requesting information. Bits 4, 3, 2, 1 indicate the 
cassette sizes. 
Tab. 11 shows a status signal indicating the number of sheets fed in a 
copying operation. A final sheet feed bit 6 indicates that the printing 
operation is completed for all the designated copy number. A resend 
request bit 5 indicates the presence of a resending request for the image 
information due to a sheet jamming or a misprint. The corresponding number 
of sheets is requested by a resend request number requesting command. 
Tab. 12 shows execution commands released by the reader to cause the 
printer to execute various operations. In response to an execution 
command, the MIMOU or the printer and the retention memory unit return the 
overall status signal shown in Tab. 3. 
In Tab. 12 there are shown a copy start command 1 for requesting the 
printer to start the copying operation, a printer stop command 2 for 
requesting the termination of copying operation, sheet feed instructing 
commands 3, 4 for instructing the sheet cassette in the single mode, a 
copy number instructing command 5 indicating the number of copies for an 
original, a multiple mode instructing mode 6 in which the second byte is 
used indicating the number of printers (1st bit for the printer 1, 2nd bit 
for the printer 2, etc.), a single mode instructing command 7, a sheet 
size instructing command 8 to be released from the reader in the multiple 
mode, and an RMU instructing mode 9 to be released from the reader in case 
the RMU is selected by the reader. 
Tab. 13 shows the contents of the 2nd byte of the retention memory unit 
instructing command 9 shown in Tab. 12, wherein bits 5, 6 indicate the 
selection of the memories A and/or B of the RMU for signal storage, while 
a bit 4 indicates the bypassing of the memories. Bits 3, 2 instruct the 
signal output from the memory A and/or B. Consequently, in the ordinary 
copying operation, the bypassing bit 4 is set. In the retention mode, the 
bypassing bit 4 is set in combination with the selection of memories for 
signal storage by the bits 5, 6. In the storage mode the bit 5 and/or 6 is 
set according to the instruction of the operation section. Also in the 
monitor mode, the bit 2 and/or 3 is set according to the instruction of 
the operation section. In the overlay mode, the bypass bit 4 and the image 
output bit 2 or 3 are set. 
The procedure o the serial communication utilizing the above-described 
commands will now be explained in further detail by a flow chart shown in 
FIG. 12. 
When the copying sequence is not in execution and there are no key entries, 
a communication shown in Tab. 13 is executed prior to a communication 
shown in Tab. 14, and there is also executed a selection of the signal 
HSBD according to a flow chart shown in Tab. 12. 
At first the reader detects whether the MIMOU and/or the retention memory 
unit is connected, by releasing the application status requesting command 
and receiving the application status signal (S16-1). After checking the 
entry of the copy start signal (S16-2), it repleases, if the MIMOU is 
connected, the printer information requesting command eight times 
corresponding to the maximum number of printers connectable to the MIMOU, 
thereby obtaining information on the printers available for printing 
operation, the printers used in the single mode and the sheet sizes 
available in the upper and lower cassettes of each printer (S16-4, 5). On 
the other hand, in the stand-alon operation in which the MIMOU is absent 
and the reader is directly connected to the printer, it releases the upper 
cassette status requesting command and the lower cassette status 
requesting command shown in Table 1 to know the sheet sizes in the upper 
and lower cassettes (S16-6). 
After the acquisition of the sheet size information etc. explained above, 
the overall status requesting command shown in Tab. 1 is released to 
obtain the overall status (S16-7). Since the copying sequence is not yet 
in progress in this stage, the overall status is only used for identifying 
the presence of a call error (S16-8). In the absence of such error, the 
program returns to the step S16-1 for requesting the application status 
and repeats the above-described procedure. 
In the presence of such error, the serviceman call error requesting command 
shown in Tab. 1 is released to know the details of said error (S16-9). 
Then the operator error requesting command shown in Tab. 1 is released to 
know the details of the operator call error (S16-10). Thereafter the 
program returns to the step S16-1 and repeats the above-described 
procedure. 
Then, in response to the depression of the copy start key, the program 
proceeds, from the copy start check ste (S16-2) to the operations shown in 
Tab. 14 indicating the communication steps during the copying sequence to 
be explained in the following. 
In the copying operation in one of the RMU modes, the reader at first 
provides the RMU with an instruction, in response to which the RMU starts 
the retention, overlay, storage or monitoring operation. 
In the following there will be explained the copying operation in the 
multiple mode in which the RMU is connected to the MIMOU. 
At first the operator enters, at the reader, the image forming conditions 
such as the sheet size, copy number (one in the storage mode) etc. and 
depresses the copy start key, whereupon the reader transmits the sheet 
size, printer number and copy number to the RMU. The sheet size is 
received by the RMU and is further transmitted to the MIMOU. The printer 
number is immediately transmitted to the MIMOU. Upon reception of the 
sheet size, printer number and copy number, the MIMOU checks the connected 
printers (however only the designated printer in the printer designation 
mode), and calculates the number of printers available for copying 
operation and having the designated sheet size. It also calculates the 
number of required printers from the copy number, and designates the 
cassettes of the required sheet size in the corresponding printers. 
After transmitting the sheet size, printer number and copy number, the 
reader sends the copy start command to the printer side. In response 
thereto, the RMU makes preparation for the copying operation except in the 
storage mode, and transmits the copy start command to the MIMOU. In 
response, the MIMOU transmits the copy start command to the printers to 
which the cassette designation has been sent. In response to the copy 
start command, each printer activates the various stations therein, and 
sends to the MIMOU a signal indicating a state ready for sheet feeding, 
when the printer becomes ready for receiving the image signal. 
The MIMOU waits until such sheet feed ready signals are received from all 
the printers required for the printing operation, and then sends a sheet 
feed ready signal to the reader through the RMU. 
The above-described procedure is executed in all the modes other than the 
storage mode. In the storage mode, the RMU, upon reception of the copy 
start command from the reader, directly sends a sheet feed ready signal to 
the reader without transmission of said command to the MIMOU. 
In all other modes than the storage mode, in response to the sheet feed 
ready signal, the reader sends a sheet feed start command to the RMU. 
Said command is transmitted, through the RMU to the MIMOU, which further 
transmits said command to the required printers. 
Except in the monitor mode or in the second and ensuing copying cycle in 
the retention mode, the reader reads the original image after releasing 
the sheet feed start command, and sends the image signal to the RMU. 
The RMU controls the image signal recording to various RMU modes. In the 
first copy in the retention mode, the image signal is stored in the memory 
of the RM and is simultaneously transmitted to the MIMOU. On the other 
hand, in the second and ensuing copying operation in the retention mode or 
in the monitor mode, no image signal is sent from the reader, and the RMU 
sends the data read from the memory as the image signal to the MIMOU. In 
the overlay mode, the image signal from the reader and the signal from the 
memory are synthesized in synchronization, and the synthesized signal is 
sent as the image signal to the MIMOU. In the storage mode the image 
signal is simply stored in the memory but is not sent to the MIMOU. 
Except in the storage mode, upon completion of each copying cycle, the 
MIMOU sends the number of copies prepared in said cy le to the reader 
through the RMU, checks whether the number of prepared copies has reached 
the copy number initially instructed by the reader, and, if all the 
required copies are made, reports that fact to the reader. On the other 
hand, if the copies of the desired number are not yet prepared, the MIMOU 
again sends the copy start command to the necessary number of printers and 
awaits that all the printers become ready for receiving the image signal. 
The reader subtracts, from the displayed copy number, the number of copies 
sent from the MIMOU through the RMU, and, upon reception of the succeeding 
sheet feed ready signal from the MIMOU, again starts the reading of the 
same original. The reader repeats this procedure until the final copy 
completion signal is received. 
In the storage mode, however, the copy number is set to "1" as explained 
before, and the image signal is not transmitted to the MIMOU from the RMU. 
The final copy completion signal is sent from the RMU to the reader 
without involving the MIMOU. 
In response to the final copy completion signal, the reader sends the 
printer stop command to the MIMOU through the RMU. In response, the MIMOU 
sends the printer stop command to all the printers in use, which in 
response terminals the function of the various devices. 
FIG. 14 shows the flow of the reader function in the multiple mode 
employing the MIMOU and the RMU. 
At first, upon depression of the copy start key by the operator, the reader 
transmits the RMU mode (S10-1), sheet size (S10-2), printer number (S10-3) 
and copy number (S10-4) to the RMU and performs initialization required 
for the copying operation. Also there is established a binary encoding 
circuit (S10-25, S10-26) in case of signal storage in the memory A or B, 
or a ternary encoding circuit (S10-27) in case of signal storage in both 
memories A and B. 
Then the reader sends the copy start command to the RMU (S10-5), and 
identifies whether the RMU monitor mode is adopted (S10-6). If not, and if 
the printers are ready for sheet feeding (S10-7), the reader sends the 
sheet feed start command to the RMU (S10-8), then starts a timer 1 
(S10-9), awaits the expiration of said timer 1 (S10-10), initiates the 
optical scanning (S10-11) and starts the original reading (S10-12). It 
then awaits the completion of the original reading (S10-13), and receives 
the number of prepared copies from the printers (S10-14). In the monitor 
mode in which the original reading operation is not required, after the 
reception of the sheet feed ready signal (S10-20), the reader sends the 
sheet feed start command (S10-21), then starts a timer 2 (S10-22), awaits 
the expiration of said timer (S10-23) and receives the number of completed 
copies from the printers (S10-14). 
Then the reader identifies whether the storage mode has been selected 
(S10-15), and, if so, sends the printer stop command to the printer side 
to terminate the copying operation (S10-24). If the storage mode has not 
been selected, the reader subtracts, from the set copy number, the number 
of copies sent from the printers (S10-16). Subsequently the reader 
identifies the completion of the copying operation by checking a 
corresponding flag (S10-17), and, upon said completion, sends the printer 
stop command to the printers to terminate the copying operation (S10-24). 
If the copying operation is not compelte, the copying operation is repeated 
until the final copy is obtained. In this case the reader identifies the 
retention mode (S10-18) and the monitor mode (S10-19), and the program 
returns to the first copying in the monitor mode (S10-20) to awaits the 
signal read-out from the memories of the RMU. In other cases the program 
returns to the first copying for other modes (S10-7) to effect the optical 
scanning. 
As explained in the foregoing, if the memory A or B alone is selected for 
signal storage in the retention memory unit, the reader automatically 
releases the image information in the state of binary signals, whereby the 
operator can easily control the system without considering possible lack 
of information. On the other hand, the reader releases a ternary image 
signal in case of the retention mode or in case the operator selects both 
memories A and B. 
Also the outputs from the memory unit are controlled by the reader, so that 
the operator can easil know the number of printed images and the burden of 
data processing in the memory unit is reduced. 
FIG. 15 shows the function of the microcomputer of the MIMOU in the image 
forming operations shown in Table 14. It is to be noted, however, that the 
control procedure starts from a step S11-1 or a step S11-7, respectively 
in the single mode or in the multiple mode. In the multiple mode, upon 
reception of the sheet size and the printer number from the reader, the 
microcomputer checks the sheet sizes in each printer (S11-1, S11-2). Said 
checking is made only on the designated printers in the designated printer 
mode, or on all the printers otherwise. 
In the present system, the MIMOU constantly exchanges various information 
with the printers and stores said information in a random access memory 
(RAM), so that the sheet sizes can be identified from said information. If 
the desired sheet size is not available in any of the available printers, 
the absence of sheet size is transmitted to the reader (S11-3, S11-4). 
If the printers with the desired sheet size are found, the microcomputer 
receives the copy number (S11-5), and calculates the number of necessary 
printers (S11-6) from the comparison of the received copy number and the 
number of printers having the required sheet size. 
Upon reception of the copy start command from the reader, the microcomputer 
sends the copy start command to the printers of thus calculated number 
(S11-7, S11-8). In the single mode, however, the copy start command is 
sent only to a specified printer. 
When all the printers start the copying function, become ready for 
receiving the image signal and report such state to the microcomputer, it 
sends an image signal receivable signal to the reader (S11-9, S11-10). 
The received image signal is simultaneously sent to the printers without 
going through the microcomputer. Each printer performs the copying 
operation, and the MIMOU identifies the occurrence of errors in each 
printer, calculates the number of prepared copies and sends said number to 
the reader (S11-12, S11-13, S11-14). In the single mode, however, the 
copying operation is repeated until the printer stop command is received 
(S11-16). The microcomputer compares the number of prepared copies with 
the copy number initially instructed by the reader, and, if said copy 
number is not yet reached, again calculates the number of necessary 
printers and re-starts the copying operation (S11-17, S11-18). 
when said copy number is reached, the microcomputer sends the final copy 
completion signal to the reader, and, in response to the printer stop 
command, sends the printer stop command to all the printers, thereby 
completing all the operation (S11-19, S11-20, S11-21). 
FIG. 16 shows the function of the microcomputer of the printer in the image 
forming operations shown in Table 14. At first, in response to the copy 
start command received from the MIMOU, the printer initiates the function 
of various stations thereof according to a determined sequence (S12-2). 
The printer of the present embodiment utilizes the electrostatic recording 
process with a photosensitive drum as explained before and therefore 
requires certain preliminary steps such as drum charging. Consequently the 
microcomputer awaits the completion of said preliminary steps, and then 
starts sheet feeding from the cassette designated by the MIMOU prior to 
the copy sheet command (S12-3, S12-4). 
The microcomputer then waits until the sheet reaches a position for 
receiving the image signal (S12-5), and sends the image signal receivable 
signal to the MIMOU (S12-6). 
Upon entry of the image signal, the microcomputer executes the copying 
operation consisting of a series of steps such as image development, image 
transfer onto the sheet, sheet discharge from the printer etc. (S12-7, 
S12-8). 
Thereafter, in response to the reception of the printer stop command, the 
microcomputer stops the various stations thereby terminating the entire 
copying operation (S12-11, S12-13), and, in response to the reception of a 
copy start command, it starts a succeeding copying operation (S12-12). 
FIGS. 17A-17F are flow charts showing the function of the retention memory 
unit. 
Said unit controls the image signal by changing the on/off state of the 
gates and the state of the selectors for the image signal. 
More specifically, two selectors 97, 98 are provided between the two input 
signals VDA, VDB and the two memories A, B to define four signal paths, 
i.e. the signal VDA to the memory A, VDA to the memory B, VDB to the 
memory A or VDB to the memory B. Also two selectors 92, 93 and two gates 
72, 73 are provided between two memories A, B and two output signals VDA, 
VDB to define four signal paths, i.e. from the memory A to the signal VDA, 
from the memory A to VDB, from the memory B to the signal VDA, or from the 
memory B to the signal VDB. Furthermore there are provided bypass gates 
for connecting the inputs VDA VDB respectively with the outputs VDA, VDB 
without going through the memories A, B. Thus the RMU controls the 
input/output paths of the video signals by controlling the status of four 
selectors 92, 93, 97, 98 and two gates 72, 73. 
FIG. 17A is a flow chart relating to the selection of four modes in the RMU 
operation. 
In response to an RMU instructing command received from the reader, the RMU 
initiates a corresponding operation (S103 in FIG. 11) Said operation is 
branched, according to the RMU instructing command (S111), into four 
modes, i.e. the retention mode (S112), overlay mode (S113), storage mode 
(S114) Or monitor mode (S115). 
FIG. 17B is an operation flow chart in the retention mode The retention 
operation is initiated I5 when the selection of the retention mode by the 
key entry in the operation section is followed by the setting of a copy 
number (S116) and the depression of the copy start key (S117). 
After the depression of the copy start key, the RMU identifies whether the 
MIMOU is included in the system (S118), and accordingly selects the 
horizontal synchronization signal HSBD. If the MIMOU is not included in 
the system, the signal BD supplied from the reader is adopted as the 
horizontal synchronization signal (S119). On the other hand, if the MIMOU 
is include, the signal HS generated by the RMU itself is adopted as the 
horizontal synchronization signal (S120). 
In the retention mode, the image signal obtained by reading an original 
image is supplied to the MIMOU for first image formation and also stored 
in the memory of the RMU, and, in the second and ensuing image formations, 
a high-speed image printing is achieved by reading the data stored in the 
memory at the first image formation, instead of repeating the original 
scanning operation. 
In said mode, the RMU at first identifies whether the copying operation is 
for a first copy (S121), then, if so, opens the bypass gate 99 to bypass 
the image signal obtained by original reading, and controls the selectors 
97, 98 in such a manner that the input signals VDA, VDB are respectively 
stored in the memories A(MA) and B(MB) (S122). Subsequently the image 
signals are bypassed (S123) and simultaneously stored in the memories 
(S124). 
For a second or ensuing copy, the selectors 92, 93 are so controlled that 
the data of the memories A(MA) and B(MB) are respectively released to the 
output lines VDA and VDB (S125), and the data are read from said memories 
A and B (S126). The output of the image signals from the memories is 
repeated until the copies of the preset number are obtained (S127). 
In the retention mode, as explained above, the reader executes the original 
reading operation only once regardless of the preset copy number, so that 
the system is quite easy to operate. 
FIGS. 17C and 17D show the operation procedure in the overlay mode. The RMU 
initiates the overlay operation when the selection of the overlay mode by 
a key entry in the operation section is followed by a memory selection 
(S128) and a setting of the copy number (S129). The memory selection step 
(S128) selects the memory or memories of which stored image is t be 
overlaid with the image signal obtained by original reading. In said step 
there is selected either the memory A, or the memory B, or the memories AB 
(a 2-page overlay of the original image and another image of 1 page stored 
in the memories A, B in the form of ternary information), or the memories 
A+B (a 3-page overlay of the original image and other images of 2 pages 
respectively stored in the memories A, B in the form of binary 
information). 
As in the retention mode, the RMU identifies, after the depression of the 
copy start key, whether the MIMOU is included in the system (S131), and 
accordingly selects the horizontal synchronization signal. As said 
synchronization signal there is adopted the signal BD supplied from the 
reader in case the MIMOU is not included (S132) or the signal HS in case 
the MIMOU is included (S133). This operation is similar to that in the 
retention mode. 
Then, the RMU controls the selectors according to the selected memories. At 
first the RMU opens the bypass gate 99 for bypassing the image signal of 
an original to be read toward the printers (S134), and controls the 
selectors 92, 93 for obtaining the desired image signal from the memory or 
memories according to the memory selection (S128). 
More specifically, there is identified whether the memory A (including 
memories AB and A+B) is selected (S135), and, if so, the selector 92 is so 
controlled that the signal of the memory A is selected as the signal VDA 
(S136). On the other hand, if the selector A is not selected, the selector 
92 is so controlled that the signal of the memory B is selected as the 
signal VDA (S137). Similarly there is identified whether the memory B 
(including the memories AB and A+B) is selected (S138), and, if so, the 
selector 93 is so controlled that the signal of the memory B is selected 
as the signal VDB (S139), and, if not selected, the selector 93 is so 
controlled that the signal of the memory A is selected as the signal VDB 
(S140). 
Then there is identified if the memories A+B are selected (S141), and, if 
selected, the selectors 92, 93 are so controlled that the signals of the 
memories A and B are respectively supplied as the signals VDB and VDA 
(S142). 
Thus, when the mode A+B is selected, the steps S136, S139 and S142 are all 
executed whereby achieving a 3-page overlay of the original image and two 
images stored in the memories (S142). 
After the above-mentioned gate controls, the RMU releases the data from the 
selected memory or memories in synchronization with the signal from the 
original image, thereby achieving the overlay operation (S143). The signal 
output is repeated until the preset copy number is reached (S144). 
FIG. 17E shows the control flow in the storage mode. After the selection of 
the storage mode by a key entry in the operation section, the RMU starts 
the storage operation in response to a memory selection (S145) and the 
depression of the copy start key (S146). The memory selecting step (S145) 
selects the memory, either A, or B or AB, for storing the signal of the 
original image. 
After the depression of the start key, the RMU selects the signal HS 
generated in the RMU as the horizontal synchronization signal for the 
image (S147), and then selects the memory for storing the signal. 
At first there is identified whether the memory A (including memories AB) 
is selected (S148), and, if selected, the selector 97 is controlled in 
such a manner that the signal VDA is stored in the memory A (S149). 
Similarly there is identified whether the memory B (including memories AB) 
is selected (S150), and, if selected, the selector 98 is so controlled 
that the signal VDB is stored in the memory B (S151). 
After such gate selection, the RMU storages the image data into the 
memories. 
FIG. 17F show the control flow in the monitor mode. After the selection of 
the monitor mode by a key entry in the operation section, the RMU starts 
the monitor operation in response to a memory selection (S153), a setting 
of the copy number (S154), and the depression of the copy start key 
(S155). The memory selection step (S153) selects the memory, either A or B 
or AB, for storing the signal of the original image. 
After the depression of the copy start key, the RMU identifies whether the 
MIMOU is included in the system (S156), and selects the signal HS 
generated in the RMU as the horizontal synchronization signal in case the 
MIMOU is included, or the signal BD supplied from the reader as said 
synchronization signal in case the MIMOU is not included in the system. 
Then the RMU identifies whether the memory A is selected (S159), and, if 
selected, controls the selector 92 in such a manner that the signal of the 
memory A is released as the signal VDA (S160). If not selected, the RMU 
controls the selector 92 in such a manner that the image of the memory B 
is released as the signal VDA (S161). 
Then the RMU identifies whether the memory A is selected (S162), and, if 
selected, controls the selector 93 in such a manner that the signal of the 
memory B is released as the signal VDB (S163). If not selected, the RMU 
controls the selector 93 in such a manner that the image of the memory A 
is released as the signal VDB (S164). 
After said selector control, the RMU releases the image signal from the 
memory or memories (S165) and repeats the signal output until the preset 
copy number of reached (S166). 
As explained in the foregoing, in an image processing system for image 
formation according to an image signal obtained from an image signal 
output unit such as an image reader, the use of an accumulating unit for 
the image signal improves the efficiency of the copying operation, enables 
simultaneous plural image formations and provides easier operability. 
TABLE 1 
______________________________________ 
1st byte 2nd byte 
Name code code 
______________________________________ 
1 Overall status request 
01 H none 
2 Operator call error request 
02 H none 
3 Serviceman call error request 
04 H none 
4 Requested resending number 
08 H none 
5 Lower cassette status request 
0B H none 
6 Upper cassette status request 
0D H none 
7 Application status request 
0E H none 
8 Printer information request 
8C H printer number 
9 Fed sheet number request 
29 H none 
______________________________________ 
*H stands for hexadecimal 
TABLE 2 
______________________________________ 
COMMAND ERROR STATUS SIGNAL 
______________________________________ 
Bit 7 1 
Bit 6 parity error 
Bit 5 -- 
Bit 4 -- 
Bit 3 -- 
Bit 2 -- 
Bit 1 -- 
Bit 0 parity error 
______________________________________ 
TABLE 3 
______________________________________ 
STATUS 1 (OVERALL STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 printer request 
Bit 5 sheet in feeding 
Bit 4 misprint present 
Bit 3 wait process in progress 
Bit 2 shut off 
Bit 1 call error present 
Bit 0 parity bit 
______________________________________ 
TABLE 4 
______________________________________ 
STATUS 2 (OPERATOR CALL ERROR STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 no toner 
Bit 5 recovered toner overflow 
Bit 4 no paper 
Bit 3 sheet jamming 
Bit 2 sorter error present 
Bit 1 -- 
Bit 0 parity bit 
______________________________________ 
TABLE 5 
______________________________________ 
STATUS 3 (SERVICEMAN CALL ERROR STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 fixing station error 
Bit 5 BD error 
Bit 4 scanner error 
Bit 3 error 
Bit 2 drum motor error 
Bit 1 no counter 
Bit 0 parity bit 
______________________________________ 
TABLE 6 
______________________________________ 
STATUS 4 (REQUESTED RESENDING NUMBER STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 requested resending number 
Bit 5 requested resending number 
Bit 4 requested resending number 
Bit 3 requested resending number 
Bit 2 requested resending number 
Bit 1 requested resending number 
Bit 0 parity bit 
______________________________________ 
TABLE 7 
______________________________________ 
STATUS 5 (LOWER CASSETTE SHEET SIZE STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 sheet size 
Bit 5 sheet size 
Bit 4 sheet size 
Bit 3 sheet size 
Bit 2 sheet size 
Bit 1 sheet size 
Bit 0 parity bit 
______________________________________ 
TABLE 8 
______________________________________ 
STATUS 6 (UPPER CASSETTE SHEET SIZE STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 sheet size 
Bit 5 sheet size 
Bit 4 sheet size 
Bit 3 sheet size 
Bit 2 sheet size 
Bit 1 sheet size 
Bit 0 parity bit 
______________________________________ 
TABLE 9 
______________________________________ 
STATUS 7 (APPLICATION STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 -- 
Bit 5 -- 
Bit 4 -- 
Bit 3 -- 
Bit 2 doubly connected units present 
Bit 1 retention memory unit present 
Bit 0 parity bit 
______________________________________ 
TABLE 10 
______________________________________ 
STATUS 8 (PRINTER INFORMATION STATUS) 
______________________________________ 
Bit 7 0 
Bit 6 printer ready 
Bit 5 my printer 
Bit 4 lower cassette sheet size bit 1 
Bit 3 lower cassette sheet size bit 0 
Bit 2 upper cassette sheet size bit 1 
Bit 1 upper cassette sheet size bit 0 
Bit 0 parity bit 
______________________________________ 
TABLE 11 
______________________________________ 
STATUS 9 (FED SHEET NUMBER STATUS) 
______________________________________ 
Bit 7 command error 
Bit 6 final sheet feeding 
Bit 5 resending request present 
Bit 4 fed sheet number bit 3 
Bit 3 fed sheet number bit 2 
Bit 2 fed sheet number bit 1 
Bit 1 fed sheet number bit 0 
Bit 0 parity bit 
______________________________________ 
TABLE 12 
______________________________________ 
1st byte 2nd byte 
Name code code 
______________________________________ 
1 Copy Start 49 H none 
2 Printer stop 4A H none 
3 Lower cassette sheet feed 
51 H none 
4 Upper cassette sheet feed 
52 H none 
5 Copy number instruction 
91 H none 
6 Multiple mode instruction 
61 H printer number 
7 Single mode instruction 
62 H none 
8 Sheet size instruction 
8F H sheet size 
9 Retention memory unit 
89 H instruction 
instruction 
______________________________________ 
TABLE 13 
______________________________________ 
RETENTION MEMORY UNIT INSTRUCTING COMMAND 
______________________________________ 
Bit 7 0 
Bit 6 storage in memory A 
Bit 5 storage in memory B 
Bit 4 image signal bypass 
Bit 3 output from memory A 
Bit 2 output from memory B 
Bit 1 0 
Bit 0 parity bit 
______________________________________ 
3 TABLE 14 
C Retention A Reader B Communication memory unit D communication 
E Multi-input-multi-output unit F communication G printer 
(1) Sheet size selection (2) Printer selection (3) Copy number 
setting (4) Select RMU mode 
##STR1## 
(1) Start memorystorage andsignal bypass (5) Copy start key 
##STR2## 
##STR3## 
(1) Check printers with required sheet size 
##STR4## 
(2) Recive sheet size 
##STR5## 
(2) Calculate number of printers (3) Instruct cassette to the 
requiredprinters 
##STR6## 
##STR7## 
##STR8## 
(4) Copy startcommands to the required printers 
##STR9## 
(1) Start prerotation (6) Start optical scan 
##STR10## 
##STR11## 
(5) Wait until allprinters become ready for feed 
##STR12## 
(7) Start original reading 
##STR13## 
##STR14## 
(6) Sheet feed startcommand to required printers 
##STR15## 
(2) Start sheet from cassette 
##STR16## 
(3) Signalbypass & storage 
##STR17## 
(7) Image signal torequired printers 
##STR18## 
(3) Image formation (8) Copy number subtraction 
##STR19## 
##STR20## 
(8) Calculate number of copies (9) Check if preset copy number is 
reached 
##STR21## 
##STR22## 
(10) Wait until allprinters become ready for feed 
##STR23## 
##STR24## 
(4) Setreaderout mode 
##STR25## 
(11) Instruct sheetfeed start to all printers 
##STR26## 
(4) Start sheetfeed from cassette (5) Start readout 
##STR27## 
(12) Image signal to all printers 
##STR28## 
(5) Image formation (9) Copy number subtraction 
##STR29## 
##STR30## 
(13) Calculate copy number 
##STR31## 
##STR32## 
(14) Check if presetcopy number is reached (15) If not, repeat 
checking from checking sheet feed ready signal 
##STR33## 
(6) Mode reset 
##STR34## 
(16) Stop all printers in use 
##STR35## 
(6) Printer stop 
In the foregoing embodiment, the reader, printer and retention memory unit 
are serially connected and the image signal from the reader is transmitted 
to the printer or the multi-input-multi-output unit always through the 
retention memory unit. In the following there will be explained another 
embodiment in which a retention memory unit of substantially same 
structure and function as explained before is connected in a different 
manner. 
FIG. 18 is an external view of another embodiment of the image processing 
system of the present invention, in which readers 401, 402 for reading an 
original image are connected, through signal lines, to a 
multi-input-multi-output unit (MIMOU) 403. Printers 405, 406 perform image 
recording on a recording material such as paper sheet in response to image 
signals transmitted from the MIMOU 402 through signal lines. A retention 
memory unit (RMU) 404 capable of storing and releasing image information 
is connected to said MIMOU 403. In contrast to the foregoing embodiment 
shown in FIG. 1, the RMU 404 is connected with the MIMOU 403 through two 
signal lines, which are connected respectively to a reader side connector 
and a printer side connector both provided on the MIMOU 403. 
In FIG. 18 the MIMOU 403 is connected to two readers 401, 402 and to two 
printers 405, 406, but the connection with more or less readers and/or 
printers is also possible. The MIMOU can be connected at maximum to four 
readers and eight printers. 
In the present embodiment, as explained above, the retention memory unit is 
not serially connected with the readers and the printers but is connected 
at the input and output thereof to the MIMOU. 
The readers and printers shown in FIG. 18 are same as those employed in the 
system shown in FIG. 1 and are therefore not explained in more detail. 
Now reference is made to FIG. 19 for explaining the control circuit of the 
retention memory unit employed in the system of FIG. 18. A microcomputer 
475 is connected through a CPU bus to a ROM 476, a RAM 477, an I/O port 
478, a timer circuit 479, and a serial communication circuit 480 which 
function in the same manner as those in the reader unit. The I/O port 478 
is connected to selectors etc. of the memory unit. The serial 
communication circuit 480 is rendered connectable in parallel manner to 
the reader side interface and to the printer side interface of said MIMOU 
403. 
The memory is composed of a memory A 485 and a memory B 486, each capable 
of storing image information of one page in A3 size. There are provided 
selectors 497, 498 to store image signals A, B constituting a ternary 
image signal in combination into the memories A and/or B. The image signal 
A is stored in a shift register 1A 482 in synchronization with a video 
clock signal, and is then stored into the memory A 485 in synchronization 
with an address generator 483. Similarly the image signal B is stored into 
the memory B 486 through a shift register 1B. The storage of two image 
signals is conducted by a common video clock signal, and the address 
generator 483 for the memories is synchronized with the video clock signal 
by means of the video enable signal. The video clock signal supplied to 
the address generator 483 is selected from that transmitted from the MIMOU 
403 and an internal clock generated in an internal generator 491. Also the 
video enable signal supplied to the address generator 483 is selected by 
the selector 488 from that transmitted from the MIMOU 403 and an internal 
signal generated in an internal generator 487. A signal HS generated in 
said video enable signal generator 487 is supplied, by a selector 474, to 
the MIMOU 403 in place of the signal BD. The above-mentioned address 
generator is utilized also at the signal read-out from the memories. The 
start command for the signal storage into or read-out from the memories A, 
B is released by the CPU 475 through the I/O port 478. 
The image signals in memories A, B are read by the address generated by the 
address generator 483, and are released as serial data through shift 
registers 2A (489), 2B (490) in synchronization with the video clock 
signal generated by the internal generator 491. The video enable generator 
487 generates the video enable signal VE at a determined timing. Selectors 
492, 493 select the lines A and/or B for releasing the image signals. 
Also, if required, said image signals are synthesized in OR circuits 494, 
495 with bypassed image signals. Besides there are provided gates 472, 473 
for synthesizing the output signals of both memories A, B with the 
bypassed image signal. The video clock signal is selected by a selector 
496 from that transmitted from the reader and an internal signal generated 
by the internal generator 491. 
Now reference is made to FIG. 20 showing the structure of the 
multi-input-multi-output unit (MIMOU). 
FIG. 20 shows the internal structure of the MIMOU 500 together with three 
readers 501-503, seven printers 511-517 and a retention memory unit 550 
connected thereto. The connecting position of said retention memory unit 
can be changed arbitrarily. 
The MIMOU 500 is composed of a multi-input-multi-output controller (MIMOC) 
520, synchronous memory boards (SBD) 521-528 respectively connected with 
the printers 511-517 and the retention memory unit 550, and an operation 
section 547. 
The MIMOC 520 is connected with the readers 501-503 and the retention 
memory unit 550, and is provided with serial circuits 531-534 to be 
respectively connected with the serial circuits of said readers and said 
retention memory unit, and further with a serial circuit 535 to be 
connected with the printers 512-517 and the retention memory unit 550. 
These circuits are controlled by a CPU 540 which functions according to a 
control program stored in a ROM 541 to control the entire MIMOU 500 
through the use of a RAM 542, an I/O port 543, an interruption controller 
544, a timer circuit 545 and a key/display driving circuit 546 which are 
connected to a CPU bus. 
As shown in FIG. 20, the MIMOC 520 is connected to the SBD's 521-528 
through a control bus CB and an image bus IB. 
The image bus IB transmits the image signals and the control signals 
therefor transmitted from the readers 501-503 and the retention memory 
unit 550. 
The control bus CB transmits the serial signals generated in the serial 
circuit 535 for communication between the MIMOU 500 and the printers 
511-517 or the retention memory unit 550, and the SBD control signal of 
the I/O port 543. 
In the present embodiment, the copy start command is given by the reader, 
and the MIMOU 500 functions as a slave to the reader. Thus, in order to 
receive the serial signals from the readers at any time, the MIMOU 500 is 
provided with a serial circuit for each reader, and all the serial signals 
from the readers are handled by the CPU 540. On the other hand, the MIMOU 
500 functions as a master to all the printers and performs the serial 
signal communication in successive manner with different printers through 
a serial circuit 535. 
The operation section 547 scans a key matrix and drives a display unit 
through the key/display driving circuit 546. 
The SBD's 521-528 are used for synchronizing the function of the printers 
with the image signals supplied from the readers. Said SBD's are same as 
those employed in the system shown in FIG. 1 and will not therefore be 
explained further. 
The connection of the retention memory unit a shown in FIG. 18 allows the 
common use thereof by the plural readers connected to the MIMOU. 
The readers can be connected with the printers in two ways, namely either 
through the MIMOU or directly with the printers, and the connection state 
is identified by application status signals to be explained later. The 
readers and the MIMOU are connected through the serial circuits having 
respective numbers as explained before, so that the MIMOU handles said 
numbers as representative of the readers. Also the MIMOU is connected with 
the printers through the synchronous memory boards, so that the MIMOU 
handles the value of the dip switch 586 on each synchronous memory board 
as a number representative of each printer. 
The retention memory unit is provided with two signal lines, one of which 
is connected to a connector at the reader side of the MIMOU while the 
other is connected to a connector at the printer side thereof. 
In case the readers are connected to the printers through the MIMOU, there 
may be selected a single mode or a multiple mode at the reader. 
In the single mode, each reader is connected by the MIMOU to a printer of a 
number same as that allotted to the reader, in which case the reader 
receives, through the MIMOU, the station status of a single printer. 
In the multiple mode, a reader can be connected through the MIMOU to 
unspecified plural printers which can be selected in the operation section 
of the reader. In the multiple mode the selection of the printers may be 
achieved by the MIMOU, in which case the MIMOU selects a necessary number 
of printers from those available at that time, depending on the preset 
copy number. In the multiple mode, the operation status of the printers 
are assembled by the MIMOU in an appropriate form and supplied to the 
reader. 
In the following explained is the process of communication in a system 
composed through the MIMOU, as the control for a connection of a reader 
and a printer is same as that of the single mode utilizing the MIMOU. 
The present embodiment provides three operating modes utilizing the 
retention memory unit (RMU) 404 shown in FIG. 18, i.e. a retention mode in 
which the image signal from the reader is stored in the retention memory 
unit 404 whereby second and ensuing copies are reproduced from the output 
signal from the retention memory unit 404, a storage mode for simply 
storing the image signal from the reader into the retention memory unit 
404, and a monitor mode for reproducing image in the printer by the image 
signal already stored in the retention memory unit 404. These modes can be 
selected by the reader, and the retention memory unit 404 functions in any 
mode in response to the command supplied from the reader. 
Now reference is made to FIG. 21 for explaining an example of setting the 
storage mode of the retention memory unit through the special operation 
section of the reader in the present system. In FIG. 21 there are shown a 
liquid crystal display device 656 and six software key 657 (SK1-SK6). The 
liquid crystal display 656 gives display corresponding to the keys 
SK1-SK6. 
When the power supply is turned on, the liquid crystal display 656 shows, 
as represented in FIG. 21(1), a message "ETC" (et cetra) in a position 
corresponding to the key SK6. The displays corresponding to the keys 
SK1-SK5 change in cyclic manner by the repeated depressions of the key 
SK6, thus enabling selection or change of the input mode according to the 
system structure. 
In response to the signals from the printers, the reader understand the 
units connected in the system and allows the user to select the input mode 
suitable for the system structure. 
When the retention memory unit 404 is connected to the system, there is 
displayed a state for selecting an RMU input mode upon repeated 
depressions of the key SK6 corresponding to the message "ETC" as shown in 
FIG. 21(2). In such state, the RMU mode is selected by depressing the key 
SK2 corresponding to a display "RMU?". If the RMU mode is not desired, the 
key SK6 corresponding to the display "ETC" is depressed whereby the 
display changes to a succeeding input mode. 
Upon depression of the key SK2 in the state shown in FIG. 21(2), the RMU 
mode is selected and the display changes as shown in FIG. 21(3). In this 
state the keys SK1-SK4 respectively correspond to the retention mode 
(high-speed retention operation utilizing memory), the storage mode 
(storage of original into memory), and the monitor mode (image reading 
from memory). 
Also in response to the depression of the key SK6 corresponding to a 
display "BACK", the input mode returns to the state shown in FIG. 21(2) 
The three RMU modes can be selected in the following manner. For example, 
the retention mode is selected by the depression of the key SK1 
corresponding to the display "RTC?", whereupon the display changes to 
"RTC!!". The mark "?" indicates that the corresponding mode is not yet 
selected, and the mark "!!" indicates that said mode has been selected by 
the depression of the corresponding SK key. 
After the retention mode is selected, the operator sets the copy number and 
depresses the copy start key as in the ordinary copier to initiate the 
high-speed retention operation utilizing the memory. 
Also the storage mode is selected by the depression of the key SK3, in the 
RMU input mode, corresponding to the message "STR?", whereupon the display 
changes, through a state shown in FIG. 21(5), to a state shown in FIG. 
21(6) awaiting the key entry. In this state the operator selects the 
memory or memories for image signal storage by depressing one of the keys 
SK1-SK3 respectively corresponding to the memory A, memory B and memories 
A and B. After the memory selection, the operator depresses the copy start 
key to initiate the storage of the original image into the memroy, and 
this operation is conducted as a preparation for the monitor mode. 
Similarly the monitor mode is selected by depression of the key SK4 
corresponding to the display "MNT?" in the RMU input mode, whereupon the 
display changes through a state shown in FIG. 10(7) to a state shown in 
FIG. 21(8), thus awaiting the key entry for selecting the memory for 
signal output. The keys SK1-SK3 respectively correspond to the memory A, 
memory B and memories A and B. After the depression of a key SK 
corresponding to the memory or memories for signal read-out, the operator 
set the copy number and depresses the copy start key to achieve the 
monitor operation. 
In the retention mode or in the monitor mode, the image reproduction is 
conducted in a printer or printers designated in the multiple or single 
mode. 
The aforementioned multiple mode can be selected, in a similar manner as 
the above-described operation of the retention memory unit 404, by 
actuating the software keys corresponding to the printer numbers displayed 
on the special operation section, but the details will not be explained 
further. 
In the present embodiment, the information between the units (between 
reader and MIMOU, between MIMOU and printer, and between MIMOU and RMU), 
except the image information, is principally conducted by serial signal 
communication. 
In these serial communications, the master function is played by the reader 
in the communication between the reader and the MIMOU, or by the MIMOU in 
the communication between the MIMOU and the printer. 
Between the MIMOU and the RMU, the master function is played by the RMU in 
an interface connected to the reader side, or by the MIMOU in an interface 
connected to the printer side. 
The master unit detects whether the opponent unit is in a state capable of 
receiving serial communication, by means of a power supply signal or a 
reception ready signal of the opponent unit, and transmits various 
commnands in serial codes if the opponent unit can receive serial 
communication. The receiving unit receives said command, checks parity 
error etc. thereof and, if said command is effective, sends back a 
corresponding information or executes a certain function if required by 
said command. 
The communication is conducted in one-to-one process, in which the master 
unit releases a command code and the receiving unit returns a status code 
corresponding to said command code. 
The command and status are same as those employed in the system shown in 
FIG. 1. 
Now reference is made to flow charts shown in FIGS. 22 to 27 for explaining 
the control procedure of various units in the present embodiment. 
When the copying sequence is not in execution and there are no key entries, 
the microcomputer of the reader performs a communication as shown in FIG. 
27 and selects the signal HSBD of the flow chart shown in FIG. 22, 
according to whether the MIMOU is connected to the system. 
At first the reader detects whether the MIMOU and/or the RMU is connected, 
by releasing the application status signal (S431). After checking the 
entry of the copy start signal (S432), it releases, if the MIMOU is 
connected, the printer information requesting command eight times 
corresponding to the maximum number of printers connectable to the MIMOU, 
thereby obtaining information on the printers available for printing 
operation, the printers used in the single mode, the sizes available in 
the upper and lower cassette of each printer and the method of connection 
of the retention memory unit to the MIMOU (S434, S435). On the other hand, 
in the stand-alone operation in which the MIMOU is absent and the reader 
is directly connected to the printer, it releases the upper cassette 
status requesting command and the lower cassette status requesting command 
shown in Table 1 to know the sheet sizes available in the upper and lower 
cassettes (S436). 
After the acquisition of the sheet size information etc. explained above in 
the presence or absence of the MIMOU, the overall status requesting 
command shown in Table 1 is released for obtaining the overall status 
(S437). Since the copying sequence is not yet in progress in this stage, 
the overall status is only used for identifying the presence of a call 
error (S438). In the absence of such error, the program returns to the 
step S431 for requesting the application status and repeats the 
above-described procedure. 
In the presence of such error, the serviceman call error requesting command 
shown in Table 1 is released to know the details of said error (S439). 
Then the operator error requesting command shown in Table 1 is released to 
know the details of the operator call error (S440). Thereafter the program 
returns to the step S431 and repeats the above-described procedure. 
The communication prior to the copying sequence is conducted in the 
above-explained manner, and, in response to the depression of the copy 
start key, the program proceeds from the copy start check step (S432) to 
the procedure shown in FIG. 23. 
FIG. 23 is a flow chart showing the control procedure of the microcomputer 
CPU of the reader in the image reading operation. 
The reader conditioned in advance by the operation section at first detects 
the presence of an RMU mode selection upon depression of the copy start 
key, and, in the presence of such selection by the operation section 
(S211), the reader releases the RMU instructing command (S212). Then it 
releases the sheet size, printer number, copy number designated by the 
operation section. The printer number is a designated number in the 
multiple mode, or is equal to the number of said reader in the single 
mode, but is not released in the RMU mode (S213, S214, S215). The printer 
number is not given in the RMU storage mode since the printer is not 
designated. Then the reader releases the copy start command (S216), and, 
in the RMU monitor mode, releases the printer stop command to terminate 
the operation (S229). Otherwise the reader awaits the entry of the sheet 
feed ready signal (S218), and, upon entry thereof, releases the sheet feed 
start command and simultaneously starts a timer 1 (S219, S220), which 
measures the time from the start of sheet feeding in the printer to the 
arrival of the sheet to an image forming position. Upon expiration of said 
timer 1 (S221), the reader starts the scanning of the optical system 
(S222) and initiates the original reading (S223). Upon completion of the 
output of the image signal (S224), the reader receives the number of 
copies (S225). In the retention or storage mode, the reader then releases 
the printer stop command to terminate the operation (S226, S227). In other 
modes, the reader subtracts the number of prepared copies (S227), then 
checks whether the final copy has been prepared (S228), and, if not, 
repeats the sheet feeding procedure. On the other hand, if the final copy 
is completed, the reader releases the printer stop command to terminate 
the operation (S229). 
FIG. 24 shows the function of the microcomputer of the MIMOU when the copy 
start command is received from the reader. 
Upon reception of the copy start command, the microcomputer checks whether 
the RMU instructing command has been received (S231), and, if received, 
releases the instruction to the RMU (S232). Also if the sheet size and the 
printer number have been received, it transmits the printer number (S233, 
S234, S235) and then the copy number (S236). It then releases the copy 
start command to the RMU (S237), thus initiating the copying operation. 
If the RMU mode is no given, the microcomputer checks the printers having 
the necessary sheet size according to the command for the printer number 
and sheet size, and, in the absence of said sheet size, it transmits a 
signal indicating the absence of sheet, thereby terminating the operation 
(S239, S240). 
Then the microcomputer sends the instruction for the upper or lower 
cassette to the printers having the necessary sheet size, and calculates 
the number of necessary printers from the printer numbers and the copy 
number (S241). Then it releases the copy start command to the required 
printers to start the copying operation (S242). Subsequently, if the 
printer stop command is received, it releases the printer stop command to 
each printer, thus terminating the operation (S243, S244). 
The microcomputer waits until all the printers become ready for sheet 
feeding, and sends the sheet feed ready signal to the reader (S245, S246). 
Then, in response to the sheet feed start command received from the reader 
(S247), it releases the sheet feed start command to the printers of a 
necessary number (S248). Subsequently, it transmits the image signal, 
received from the reader, to all the printers to which the sheet feed 
start command have been sent (S249). The microcomputer executes error 
check, then, in the presence of an error (S250), executes an error process 
(S251), and calculates the number of copies and reports it to the reader 
(S252). The microcomputer then checks whether all the copies have been 
completed, and, if so, sends the final copy completion signal to the 
reader and awaits the printer stop command. If not, the microcomputer 
repeats the procedure from the step of calculating the number of necessary 
printers (S253, S254). 
FIG. 25 shows the function of the microcomputer of the printer in the image 
forming operation. In response to the copy start command received from the 
MIMOU, the printer activates various stations thereof according to a 
determined sequence (S261, S262). 
The printer of the present embodiment utilizes the electrostatic recording 
process with a photosensitive drum as explained before and therefore 
requires certain preliminary steps such as drum charging. Consequently the 
microcomputer awaits the completion of said preliminary steps, and then 
starts sheet feeding from the cassette designated by the MIMOU prior to 
the copy start command (S263, S264). 
The microcomputer then waits until the sheet reaches a position for 
receiving the image signal (S265), and sends the image signal receivable 
signal to the MIMOU (S266). 
Upon entry of the image signal, the microcomputer executes the copying 
operation consisting of a series of steps such as image development, image 
transfer onto the sheet, sheet discharge from the printer etc. (S267, 
S268). 
Then it detects the error in the copying operation, and sends the relative 
information to the MIMOU (S269, S270). 
Thereafter, in response to the reception of the printer stop command, the 
microcomputer stops the various stations thereby terminating the copying 
operation (S271, S272), and, in response to the reception of a copy start 
command, it start a succeeding copying operation. 
FIG. 26 shows the function of tne microcomputer of the retention memory 
unit (RMU) 404 upon receiving the copy start command. As the MRU is 
connected with the MIMOU 403 through the reader side connector and the 
printer side connector, the command from the reader is received through 
the MIMOU and the interface at the printer side, while the command to the 
printer is transmitted through the interface at the reader side. Also in 
response to a status request command from the MIMOU, the MRU releases the 
status signal through the interface at the printer side and receives the 
status signals from the printers through the MIMOU and the interface at 
the reader side. 
The copying flow is conducted as follows. The RMU at first detects if the 
RMU mode is selected (S401), and, in case of image memory command in the 
retention or storage mode, selects the memory or memories for image 
storage according to the selected RMU mode (S402). In case of the 
retention mode, both memories A (485) and B (486) are selected (S403), and 
there is released the sheet feed ready signal (S404), in response to which 
the reader releases the sheet feed start command and the image signal. The 
RMU receives and stores said signals (S405, S406). The signal storage is 
completed by the reception of the subsequent printer stop command (S408), 
but the signal output in the retention mode is started in the same manner 
as the reader through the interface at the reader side. 
At first the RMU again transmits, to the MIMOU, the printer number, sheet 
size and copy number already received at the start of funcgion S409, S410, 
S411), then releases the copy start command (S412), and selects the memory 
or memories for signal output by the RMU instructing command. In the 
retention mode both memories A and B are selected for signal output 
(S413). Then, in response to the entry of the sheet feed ready signal from 
the MIMOU, the RMU releases the sheet feed start command (S414, S415) and 
starts the timer 1 which was already explained in the function of the 
reader (S416). Upon expiration of said timer 1, the RMU releases the image 
signal from the memories (S417, S418). Upon completion of the output of 
the image signal (S419), the MRU receives the number of prepared copies 
(S420), checks whether the final sheet feed is completed (S421), and, if 
not, repeats the procedure from the step of checking the sheet feed ready 
signal. On the other hand, if complete, the printer stop command is 
released to terminate the copying operation (S422). 
The present invention has been explained by reference to two preferred 
embodiments thereof, but it should be understood that various 
modifications are possible within the scope and spirit of the appended 
claims.