Image forming apparatus

An image forming apparatus is provided which forms an image on a sheet on the basis of image data selectively received from a plurality of host apparatuses. The image forming apparatus comprises a plurality of input/output ports, connected to the respective host apparatuses for receiving image data from the host apparatuses, keys for setting priority orders of the plurality of input/output ports, memories for storing the priority orders set by the keys, and a CPU for selecting one of the input/output ports in accordance with the priority orders stored in the memories, if image data is received simultaneously from two or more of the host apparatuses, a memory and photosensitive assembly for receiving image data from the input/output ports selected by the keys and for forming an image corresponding to the received image data.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image forming apparatus (e.g., a laser 
printer or an electronic copying machine) for forming an image in 
accordance with image data supplied from a host apparatus. 
2. Description of the Related Art 
Conventionally, an image forming apparatus (such as a laser printer or an 
electronic copying machine) is connected to a host apparatus (such as a 
computer or an image reader), and forms an image on a sheet (i.e., an 
image forming medium) in accordance with image data supplied from the host 
apparatus. This type of image forming apparatus is expensive and yet it is 
not often accessed by the host apparatus. Therefore, effective use is not 
made of the image forming apparatus. 
This problem may be solved by providing a multi-port type host interface 
for the image forming apparatus, so as to permit the image forming 
apparatus to be accessed by a plurality of host apparatuses. More 
specifically, the multi-port type interface incorporates a priority 
circuit that causes the image forming apparatus to be used in accordance 
with priority orders which are previously assigned to the ports of the 
interface circuit. If the image forming apparatus is simultaneously 
accessed by two or more host apparatuses, in other words, if it is 
simultaneously supplied with image data from two or more host apparatuses, 
the host apparatuses are selected in accordance with the priority orders 
and are thus connected to the image forming apparatus in accordance with 
the degree of emergency. By using the image forming apparatus on this time 
divisional basis, it is intended that efficient use may be made of the 
image forming apparatus. 
However, in these conventional systems the priority orders assigned to the 
ports of the multi-port type interface are fixed. Therefore, if the 
operator wants to alter the priority orders, it is necessary to change the 
connection of cables. This operation is very troublesome and time 
consuming. Further, even if the operator wants the image forming apparatus 
to be temporarily accessed by a particular host apparatus, this cannot be 
done easily. That is, the operator must first turn off the image forming 
apparatus and then modify the cable connection, for temporary priority use 
of the particular host apparatus. Therefore, from a practical standpoint 
such temporary priority use is impossible. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an image 
forming apparatus which permits temporary priority use of a particular 
host apparatus. 
The foregoing and additional objects are attained by providing an image 
forming apparatus which forms an image on a sheet on the basis of image 
data selectively received from a plurality of host apparatuses. The image 
forming apparatus comprises a plurality of input/output ports, connected 
to the respective host apparatuses for receiving image data from the host 
apparatuses, keys for setting priority orders of the plurality of 
input/output ports, memories for storing the priority orders set by the 
keys, and a CPU for selecting one of the input/output ports in accordance 
with the priority orders stored in the memories, if image data is received 
simultaneously from two or more of the host apparatuses, a memory and 
photosensitive assembly for receiving image data from the input/output 
ports selected by the keys and for forming an image corresponding to the 
received image data.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a perspective view showing a laser printer apparatus (i.e., an 
image forming apparatus) according to a preferred embodiment of the 
present invention, while FIG. 2 is a longitudinal sectional view showing 
the internal construction of the laser printer apparatus. 
Referring to these Figures, laser printer apparatus 1 includes a housing 5. 
The rear portion of the upper surface of housing 5 is raised, with a 
slanted portion located between the raised portion and the other portions. 
In the center of the upper surface, hollow section 6 is located. This 
hollow section communicates with the interior of housing 5 and serves as a 
paper discharge section. A paper discharge tray 8 movably supported by 
jogger 7 is provided in hollow section 6. On the upper surface of housing 
5, operating panel 9 is located on the right side of hollow section 6 and 
three IC card-insertion ports 11 are located on the left side of hollow 
section 6. 
As is shown in FIG. 3, operating panel 9 (which serves as both a setting 
means and an interruption means) comprises: LCD 9a (i.e, a liquid crystal 
display) for indicating the number of copies, the mode of the apparatus 1, 
guide messages, etc; LED displays 9b for indicating the conditions of 
apparatus 1 with LEDs (light emitting diodes); and switches 9c for setting 
apparatus 1. LED displays 9b include: an "ON LINE" display for indicating 
whether apparatus 1 is in the on-line mode or in the off-line mode (i.e., 
it indicates whether apparatus 1 is electrically connected to a given 
external device); a "READY" display for indicating whether or not 
apparatus 1 is ready for printing; a "DATA" display for indicating whether 
o not image data is being transferred; an "OPERATOR" display for 
indicating a request for an operator call; a "SERVICE" display for 
indicating a request for a service man call; and a "MODE" display for 
indicating whether apparatus 1 is in the automatic mode or in the manual 
mode. 
Switches 9c include a menu key, a value key, an input key, a ten-key pad 
(not shown), etc. The menu key is made up of a "NEXT ITEM" key and a 
"PRECEDING ITEM" key. A plurality of pieces of menu information displayed 
in the left half of LCD 9a are changed with an increment of 1 upon 
depression of the "NEXT ITEM" key of the menu key, and are changed with a 
decrement of 1 upon depression of the "PRECEDING ITEM" key of the menu 
key. The value key is also made up of a "NEXT ITEM" key and a "PRECEDING 
ITEM" key. A plurality of pieces of value information displayed in the 
right half of LCD 9a in correspondence to the menu information are changed 
with an increment of 1 upon depression of the "NEXT ITEM" key of the value 
key, and are changed with a decrement of 1 upon depression of the 
"PRECEDING ITEM" key of the value key. The menu information and the value 
information are displayed in a cyclical fashion, by operating the 
respective "NEXT ITEM" and "PRECEDING ITEM" keys. The operator selects a 
desirable operation mode by operating the menu and value keys and commands 
the start of the selected operation mode by operating the input key. 
Further, the operator can enter the value information used for setting the 
number of copies to be produced. 
Paper discharge tray 12 is located at the front of housing 5, and manual 
insertion tray 13 is located at the rear of housing 5. Paper sheet 
detector 26 is arranged on the bottom of manual insertion tray 3. If a 
paper sheet (i.e., a medium on which an image is formed) is inserted from 
manual insertion tray 13, paper sheet detector 26 detects it and supplies 
a detection signal to CPU 50 (FIG. 4) to be explained later. 
As is shown in FIG. 2, photosensitive body 15, which is in the form of a 
drum and serves as an image carrier, is located in the center of the 
internal region of housing 5. Around photosensitive body 15, the following 
elements are arranged: charging unit 16, laser system 17, developing unit 
18, transfer unit 19, separation unit 20, cleaning unit 21, and 
discharging unit 22. These elements are arranged in the rotating direction 
of photosensitive body 15 in the order mentioned. 
In the inside of housing 5, image support transportation path 24 extends 
from the rear to the front of apparatus 1, via image transfer section 23 
located between photosensitive body 15 and transfer unit 19. Paper sheet P 
which is automatically supplied from paper sheet cassette 25 by means of 
paper supply roller 28 and paper feed roller 29b is conveyed to image 
transfer section 23. Likewise, paper sheet P which is manually supplied 
from manual insertion tray 13 via paper feed roller 29a is conveyed to 
image transfer section 23. 
In image support transportation path 24, a pair of aligning rollers 30 are 
arranged on the upstream side of image transfer section 23; and fixing 
unit 31, discharge paper selector 32 and a pair of paper discharge rollers 
33 are arranged on the downstream side of image transfer section 23. 
At the terminating end of image support transportation path 24, branch path 
35 is provided. Along this branch path, paper sheet P directed thereto by 
discharge paper selector 32 is conveyed to hollow section 6 (i.e., a paper 
discharge section). A pair of paper discharge rollers 34 are provided in 
branch path 35, so as to guide paper sheet P to hollow section 6. 
In FIG. 1, reference numeral 40 denotes a lower cover, numeral 41 denotes a 
front cover, numeral 42 denotes an upper cover, numeral 43 denotes a right 
cover (or a door) which can be opened or closed, numeral 44 denotes a left 
cover, numeral 45 denotes a lever for opening or closing the right cover, 
and numeral 46 denotes a lever for opening or closing an upper unit. In 
FIG. 2, reference numerals 47 and 49 denote circuit boards on which 
printer circuits for controlling the operation of printer apparatus 1 are 
formed, and numeral 48 denotes three circuit boards on which printer 
controlling circuits for controlling the printer circuits are formed. (In 
other words, circuit boards 48 constitute a printer control section.) 
Three connectors (not shown) are attached to the ends of three circuit 
boards 48, respectively, thereby constituting IC card-insertion ports 11 
adapted for insertion of IC cards 65, 66 and 67 (FIG. 4). 
To form an image, photosensitive body 15 is rotated and uniformly charged 
by charging unit 16. Then, laser system 17 partially exposes 
photosensitive body 1 to light on the basis of image signals, thereby 
forming an electrostatic latent image on photosensitive body 15. 
Developing unit 18 develops the electrostatic latent image on 
photosensitive body 15 by use of a two-component developer containing 
toner and carrier, and the developer image, thus obtained, is conveyed to 
image transfer section 23. 
Simultaneous with the formation of the developer image, paper sheet P, 
which is automatically taken out of paper sheet cassette 25 o manually 
inserted from manual insertion tray 13, is conveyed to image transfer 
section 23. At this image transfer section, transfer unit 19 transfers the 
developer image from photosensitive body 15 to paper sheet P. Thereafter, 
separation unit 20 separates the paper sheet from photosensitive body 15 
and then the paper sheet is conveyed to fixing unit 31 along image support 
transportation path 24. After the fused fixing of the developer image to 
paper sheet P, paper sheet P is conveyed from fixing unit 31 to discharge 
paper selector 32. By this selector, the discharge direction of paper 
sheet P is determined thus, paper sheet P is directed to either paper 
discharge tray 8 or tray 12. 
After the developer image is transferred to paper sheet P, photosensitive 
body 15 is cleared of its residual toner by cleaning unit 21, so that 
photosensitive body 15 is ready for the next copying operation. 
FIG. 4 is a block circuit diagram showing the main portion of the electric 
circuit of printer control section 48. Referring to FIG. 4, CPU 50 
controls the entire image forming apparatus. ROM 51 stores a control 
program, on the basis of which CPU 50 operates. ROM 51 also stores 
identification number data (ID number data) which is checked when data is 
altered. It further stores data regarding paper sheet P, such as the data 
representing the right margin, left margin, paper type, etc. RAM 52 is 
used as a page buffer for temporarily storing image data supplied from 
host apparatuses 58. (In FIG. 4, only one host apparatus is illustrated 
for simplicity.) RAM 52 is also used as a work buffer of CPU 50. Expanded 
memory 53 is a large-capacity memory and is used if the amount of image 
data supplied from host apparatus 58 is large, as in the case of bit map 
data, and if RAM 52 cannot store one-page data of the supplied image data. 
Video RAM 54 is used as a scan buffer for storing image data developed as 
a bit image, and the image data output from this video RAM is supplied to 
serial-parallel conversion circuit 55. Serial-parallel conversion circuit 
55 converts the image data (which is developed as a bit image in video RAM 
54 and is supplied to conversion circuit 55 as parallel data) into serial 
data, and supplies the converted serial data to printer circuits 47 and 
49. 
Host interface 57 transfers data between host apparatus 58 and printer 
control section 48. Transfer line 59, which connects interface 57 and host 
apparatus 58 to each other, comprises two types of lines, namely a serial 
transfer line and a parallel transfer line. One of these lines is 
selectively used in accordance with the type of data transferred between 
host apparatus 58 and interface 57. Details of the host interface will be 
explained more fully later. 
Printer interface 60 is provided in the control signal line between printer 
control section 48 and printer circuits 47 and 49. The detection signal of 
paper sheet detector 26 is supplied to CPU 50 through this printer 
interface. 
Operating panel-controlling circuit 56 controls operating panel 9 such that 
a guide message is correctly shown on LCD 9a, such that LED displays 9b 
are correctly turned on or off or are correctly flickered, and such that 
the data entered through switches 9c is reliably supplied to CPU 50. 
Internal bus 61 is a bus through which data is transferred between the 
following elements: CPU 50, ROM 51, RAM 52, expanded memory 53, video RAM 
54, operating panel-controlling circuit 56, host interface 57, printer 
interface 60, and IC cards 65-67. 
IC cards 65-67 are volatile memories and are made of battery-backup type 
static RAMs, E.sup.2 PROMs, EPROMs, mask ROMs, or the like. The IC cards 
are colored in accordance with the memory types and the data which they 
store. For instance, an IC card made of a mask ROM and storing fonts is 
colored in blue, an IC card made of a static RAM and storing emulation 
data is colored in orange, etc. Therefore, the memory types and the data 
stored in IC cards 65-67 are readily known by merely glancing at the IC 
cards. 
As is shown in FIG. 5, host interface 57 comprises: CPU 70; ROM 71; RAM 72; 
input/output port 73a, 73b, . . . , 73n respectively connected to host 
apparatuses 58a, 58b, . . . , 58n; input/output port 74 connected to 
internal bus 61; and external bus 75 for connecting these elements 
together. 
Referring to FIG. 5, CPU 70 (which serves as both a selecting means and an 
interruption means) controls the whole of host interface 57. ROM 71 stores 
a control program, on the basis of which CPU 70 operates. RAM 72 (which 
serves as a storage means) temporarily stores data supplied from host 
apparatus 58. It is also used as a work buffer of CPU 70, and is further 
used for storing a priority order table representing the priority orders 
of input/output ports 73a, 73b, . . . , 73n. In the case illustrated in 
FIG. 5, input/output port #1 is defined as having priority order n (i.e., 
the lowest priority order), and input/output port #2 is defined as having 
priority order 2 (i.e., the second priority order). (See FIG. 5) 
Input/output ports 73a, 73b, . . . , 73n each serve as a connection means, 
and host apparatuses 58a, 58b, . . . , 58nare connected to the respective 
input/output ports. The input/output ports and the host apparatuses are 
connected by means of transfer lines 59a, 59b, . . . , 59n, respectively. 
As mentioned above, each of transfer lines 59a, 59b, . . . , 59n comprises 
both serial and parallel transfer lines, and these two types of transfer 
lines are used in accordance with the type of data to be transmitted. 
Input/output port 74 connects host interface 57 to internal bus 61 of 
printer control section 48. In host interface 57, one of input/output port 
73a, 73b, . . . , 73n is selected in accordance with the priority orders, 
and data is supplied from the selected input/output port to RAM 52 etc. of 
printer control circuit 48. This data is supplied through input/output 
port 74. Further, input/output port 74 receives data from printer control 
circuit 48 and sends this data to CPU 70. 
The priority orders are set as described below. 
The contents in the priority order table, shown in FIG. 6, can be freely 
altered by operating switches 9c of operating panel 9. To alter the 
contents, the operator follows the procedures below. 
First, the operator cyclically changes what is shown in the message display 
region on the left side of LCD 9a by operating either the "NEXT ITEM" key 
or the "PRECEDING ITEM" key of the menu key of operating panel 9, until 
the message "PORT SEQ n:" used for setting the priority order of 
input/output port #n is shown in the message display region. In the state 
where the message "PORT SEQ n:" is displayed in the message display 
region, the operator cyclically changes the priority order shown in the 
input region on the right side of LCD 9a by operating either the "NEXT 
ITEM" key or the "PRECEDING ITEM" key of the value key, until the priority 
order desired by the operator by the operator, e.g., "1", is shown in the 
input region. In the state where the desirable priority order "1" is shown 
in the input region, the operator depresses the input key. By depressing 
the input key, the desirable priority order "1" is read by control circuit 
56, and is then supplied, via internal bus 61 and input/output port 73a, 
to CPU 70 of host interface 57 under the control of CPU 50. Thereafter, 
under the control of CPU 70, the desirable priority order is stored in the 
priority order table of RAM 72, in association with the input/output port 
number selected with the menu key. In this fashion, input/ output port "n" 
is defined as having priority order "1". By following similar procedures, 
the priority orders of the other input/output ports can be set and stored 
in the priority order table. 
In the case of the image forming apparatus of the present invention, the 
way of setting priority orders is not limited to the above-mentioned 
procedures. The apparatus further comprises a means for giving the highest 
priority order to any one of the input/output ports by interrupting the 
predetermined priority orders. For this purpose, the operator cyclically 
changes what is shown in the message display region on the left side of 
LCD 9a by operating either the "NEXT ITEM" key or the "PRECEDING ITEM" key 
of the menu key, until the message "INT PORT:" (which is used for setting 
a high priority order to a particular input/output port) is shown in the 
message display region. In the state where the message "INT PORT:" is 
displayed in the message display region, the operator cyclically changes 
the priority order shown in the input region on the right side of LCD 9a 
by operating either the "NEXT ITEM" key o the "PRECEDING ITEM" key of the 
value key, until a high priority order desired by the operator, e.g., "n", 
is shown in the input region. In the state where the desirable priority 
order "n" is shown in the input region, the operator depresses the input 
key. By depressing the input key, the desirable priority order "n" is read 
by control circuit 56, and is then supplied, via internal bus 61 and 
input/output port 73a, to CPU 70 of host interface 57 under the control of 
CPU 50. Thereafter, under the control of CPU 70, the image data 
corresponding to the input/output ports starting from the input number "n" 
is supplied to printer control section 48, prior to the image data 
corresponding to the other input/output ports. 
At this time, the operator can select whether the image data corresponding 
to the input/output ports starting from the input number "n" should be 
supplied after the end of the processing performed then, or whether the 
image data should be supplied, with the processings interrupted. In other 
words, the operator chooses whether he would like to wait for the 
processings to be completed before starting the supply of the image data, 
or whether he would like to interrupt the processings to start the supply 
of the image data (a predetermined time is required before the 
interruption of the processings). Hereinafter, the former case will be 
referred to as a "EOJ" mode, and the latter case will be referred to as a 
"TIMER" mode. The operator can designate one of these modes by use of 
operating panel 9. More specifically, the operator cyclically changes what 
is shown in the message display region on the left side of LCD 9a by 
operating either the "NEXT ITEM" key or the "PRECEDING ITEM" key of the 
menu key, until the message "BLOCK:" used for designating the switching 
timings of the input/output ports is shown in the message display region. 
In the state where the message "BLOCK:" is displayed in the message 
display region, the operator cyclically changes the mode-indicating 
message shown in the input region on the right side of LCD 9a by operating 
either the "NEXT ITEM" key or the "PRECEDING ITEM" key of the value key, 
until the message desired by the operator, e.g., "EOJ", is shown in the 
input region. In the state where the desired message "EOJ" is shown in the 
input region, the operator depresses the input key. By depressing the 
input key, the input message "EOJ" is read by control circuit 56, and is 
then supplied, via internal bus 61 and input/output port 73a, to CPU 70 of 
host interface 57 under the control of CPU 50. Thereafter, under the 
control of CPU 70, the designated input/output port is enabled at the end 
of the processings or job which is then being performed, i.e., at the time 
when an EOJ code designating the end of the job has been supplied. 
A description will now be given, with reference to the flow chart shown in 
FIG. 7, as to how the image forming apparatus is accessed by each of host 
apparatuses 58a, 58b, . . . , 58n. 
First of all, in Step T1 it is determined whether or not input/output port 
#n-1, which has the first priority order, has received data (PR1 
reception), while referring to the priority order table (FIG. 6) provided 
in RAM 72. If it is determined that input/output port #n-1 has not 
received any data, then the flow advances to Step T2. In Step T2, it is 
determined whether or not input/output port #2, which has the second 
priority order, has received data (PR2 reception). Similarly, it is 
checked, on the basis of the priority orders stored in the priority order 
table, whether or not the remaining output ports have received data. If, 
after examining data reception with respect to input/output port #1 having 
the lowest priority order (Step T4), it is found out that each 
input/output port does not receive any data, then the flow returns to Step 
T1, so as to repeat the same checks. The checks are repeated until data is 
received at one of the input/output ports. 
Let it be assumed that, in Step T2, input/output port #2 having the second 
priority order receives data. In this case, the data received by 
input/output port #2 is supplied to input/output port #0 (Step P1). Under 
the control of CPU 50, the data is then supplied from input/output port #0 
to RAM 52, via internal bus 61 of printer control section 48, and is 
stored in RAM 52. Next, in Step P2, a check is made with respect to the 
mode that determines the switching timings of input/output ports. If it is 
determined in Step P2 that the mode is the "EOJ" mode, then the flow 
advances to Step P3, in order to check whether or not the reception data 
is an EOJ code. If the reception data is not the EOJ code, it is 
determined that the data transfer has not yet been completed. Therefore, 
the flow returns to Step P1 to repeat the same procedures, and the data 
reception and the data supply to input/output port #0 are repeated until 
the EOJ code is received. When this EOJ code has been received, the flow 
advances to Step P4. If it is determined in Step P2 that the mode is the 
"TIMER" mode, the flow advances to Step P5, to check whether or not a time 
preset for the data transfer is over. More specifically, a certain time is 
preset for the transfer of each image data, and a timer (not shown) starts 
counting from the start of the data transfer. By use of the timer, it is 
determined in Step P2 whether or not the image data is transferred within 
the preset time. If the data transfer is determined as having been 
performed within the prescribed time, the flow returns to Step P1 to 
repeat the above procedures, and the data reception and the data supply to 
input/output port #0 are repeated until a "time over" state is detected. 
If this "time over" state is detected, the data transfer is stopped, and 
the flow advances to Step P4. 
In Step P4, it is checked whether or not interruption has been commanded. 
If the interruption is not commanded, the data reception processings are 
stopped. In this case, the flow returns to Step T1, and the above 
procedures are repeated until data is received at one of the input/output 
ports. 
If it is found out in Step P4 that interruption has been commanded, the 
flow branches to the processings for the input/output port or ports which 
should be selected prior to the others. In other words, the flow branches 
to one of interrupt entries 1 to n. Since it is natural that the 
input/output port or ports designated by the interruption receive data, 
data reception processings are performed with respect to the ports. This 
means that the data reception processings with respect to the input/output 
ports designated by the interruption are carried out, prior to any other 
data reception processings. 
As mentioned above, according to the present invention, the priority orders 
of input/output ports 73a, 73b, . . . , 73n to which host apparatuses 58a, 
58b, . . . , 58n are respectively connected can be freely set or altered 
by use of operating panel 9. Therefore, the connections of cables 59a, 
59b, . . . , 59n need not be changed even in the case where the priority 
orders of input/output ports 73a, 73b, . . . , 73n are altered. Therefore, 
the priority orders of the host apparatuses connected to input/output 
ports 73a, 73b, . . . , 73n can be easily set or altered, thus providing 
for efficient use. 
Even when the apparatus is operating in accordance with the predetermined 
priority orders, interruption of the processings can be commanded, so as 
to select any one of the input/output ports 73a, 73b, . . . , 73n. 
Therefore, a particular host apparatus can be temporarily used, prior to 
the others. 
In the above fashion, image data is received from the input/output port 
selected by host interface 57. The image data is developed as bit map data 
and is then supplied to the printer for the formation of an image. A 
description will now be given of this image forming operation, with 
reference to the data transfer processings shown in FIG. 9. 
First, a description will be given as to how data transfer is performed 
between printer circuits 47 and 49 and printer control section 48. FIG. 9 
shows the procedures performed for this data transfer. (1) When the 
printer becomes ready for printing, a print request is made by the 
printer. (2) If, at this time, image data to be printed is already 
prepared, printer control section 48 supplies a print command to the 
printer in response to the print request. (3) In response to the print 
command, the printer outputs a VSYNC request that requests synchronization 
in the vertical direction, i.e., in the conveyance direction of paper 
sheet P. (4) In response to the VSYNC request, printer control section 48 
supplies a VSYNC command to the printer. This VSYNC command determines the 
timing at which laser system 17 starts forming an electrostatic latent 
image on photosensitive body 15 and is output when paper sheet P, supplied 
from either paper sheet cassette 25 or manual insertion tray 13, has 
reached a predetermined point in image support transportation path 24. 
This point is determined in such a manner that the time which is required 
for paper sheet P to be conveyed from that point to image transfer section 
23 is the same as the time which is required for the electrostatic latent 
image formed on photosensitive body 15 to reach image transfer section 23 
after being developed by developing unit 18. (5) Next, the printer which 
receives the VSYNC command supplies a HSYNC request to printer control 
section 48, after laser system 15 is brought to its initial position with 
respect to the horizontal direction, i.e., the direction perpendicular to 
the conveyance direction of paper sheet P. (6) In response to the HSYNC 
request, printer control section 8 supplies the image data, which is 
developed in the form of a bit image, to the printer. After the image data 
corresponding to one page is transferred in this fashion, the image 
forming operation is stopped. 
Next, a detailed description will be given, with reference to the flow 
charts shown in FIGS. 8A and 8B, as to how printer control section 48 
operates by utilization of the data transfer mentioned above. 
Let it be assumed that the image forming apparatus is in the off-line 
state. If CPU 50 determines in Step S1 that the apparatus is in the 
off-line state, a check is made in Step S2 to see whether or not the 
printing of the image data supplied from host apparatus 58 has been 
finished. If the printing has not yet been finished, the flow advances to 
Step S2 to continue the printing. If the printing has been finished, then 
Steps S1 and S2 are repeatedly executed, whereby the apparatus is set in 
an "idling condition" and waits for the on-line state. 
If CPU 50 determines in Step S1 that the image forming apparatus is in the 
on-line state, then a check is made in Step S3 to see whether or not the 
data supplied from host apparatus 58 is a command. If the data is a 
command, the apparatus performs the operation corresponding to the command 
(Step S4). If the data is not a command, the flow advances to Step S5, 
skipping Step S4. The command mentioned above is for determining the 
attributes of the succeeding data and for executing such printer control 
as does not need data exchange. In Step S5, a check is made to see whether 
or not the page buffer, which is provided in RAM 52 as a data reception 
buffer, is full. If the page buffer is not full, a check is made in Step 
S6 whether or not the data supplied from host apparatus 58 is image data. 
If the data is not image data, then the flow returns to Step S1, and the 
above steps are repeatedly executed until either a command or image data 
is received. If, in this condition, it is determined in Step S6 that image 
data has been received, the received image data is stored in the page 
buffer (Step S7). Next, a check is made in Step S8 to see whether or not 
image data corresponding to one page has been stored in that page buffer. 
If the one-page image data has not yet been stored, the "DATA" lamp 
included in LED displays 9b of operating panel 9 is made to flicker (Step 
S10). The flow then returns to Step S1, and the above steps are repeatedly 
executed until the one-page image data is stored in the page buffer. If, 
in this condition, it is determined that the one-page image data has been 
stored in the page buffer, the "DATA" lamp is turned off (Step S9) and the 
data receiving processings are stopped. Thereafter, the flow advances to 
the printing processings starting from Step S12. If it is determined in 
Step S5 that the page buffer is full, the data receiving processings are 
stopped (Step S11), and the flow advances to the printing processings 
starting from Step S12. If the "DATA" lamp did not flicker but instead 
uncontinuously lit, it would be impossible for the operator to know 
whether the data is still being transferred or whether something is wrong 
with the apparatus. In the present invention, however, the "DATA" lamp 
flickers while the data receiving processings are being performed, so that 
the operator readily may identify the condition of the apparatus. 
When the one-page image data has been stored in the page buffer, a check is 
made in Step S12 to see whether or not the scan buffer, which is provided 
in video RAM 54, is full. If it is determined that the scan buffer is not 
full, the image data stored in the page buffer is converted from a 
character image to a bit image under the control of CPU 50, and the 
converted image data is stored in video RAM 54 (Step S13). If it is 
determined that the scan buffer is full, the flow advances to Step S14, 
skipping Step S13. In Step S14, a check is made to see whether or not a 
print command has been already issued. If the print command has already 
been issued, then the flow advances to Step S20, skipping Steps S15 
through S19 (in these steps, the processing for issuing a print command is 
performed). If the print command has not yet been issued, a check is made 
in Step S15 to see whether or not the printer has already output a print 
request. If no print request has been outputted, it is determined that the 
printer is not ready for printing. Thus, the flow returns to Step S1, and 
the above steps are executed once again until a print request is output by 
the printer. If the print request has been outputted, a check is made in 
Step S16 to see whether paper sheet P has been conveyed from paper sheet 
cassette 25 or from manual insertion tray 13. Specifically, a check is 
made to see whether or not paper sheet detector 26 at the bottom of manual 
insertion tray 13 has detected a paper sheet. If paper sheet detector 26 
has detected a paper sheet, it is determined in Step S17 that paper sheet 
has been manually inserted through tray 13. Therefore, paper feed roller 
29a is driven to guide paper sheet P from manual insertion tray 13 to 
image transfer section 23. If no paper sheet is detected by paper sheet 
detector 26 in Step S16, it is determined in Step S18 that paper sheet P 
has been conveyed from paper sheet cassette 25. Therefore, paper feed 
roller 29b is driven to guide paper sheet P from paper sheet cassette 25 
to image transfer section 23 (Step S18). 
After identifying the supply source of paper sheet P in the above manner, a 
print command is supplied to the printer (Step S19). Next, a check is made 
in Step S20 to see whether a VSYNC command has already been issued. If the 
VSYNC command has not yet been issued, a check is made in Step S21 to see 
whether or not the printer has already outputted a VSYNC request. If the 
VSYNC request has not yet been outputted, the flow returns to Step S1, and 
the above steps are executed once again until a print request is made by 
the printer. If it is determined in Step S21 that a print request has been 
made by the printer, a VSYNC command is supplied to the printer in Step 
S22, so that the printer is supplied with the information representing the 
timings at which an electrostatic latent image is formed with laser system 
17. In this condition, the flow returns to Step S1 to wait for the printer 
to output an HSYNC request. 
If it is determined in Step S20 that the VSYNC command has already been 
outputted, then a check is made in Step S23 to see whether or not data is 
being transferred. If the data is not being transferred, a check is made 
in Step S24 to see whether an HSYNC request has been made by the printer. 
If the HSYNC request has not yet been made, the flow returns to Step S1, 
and the above steps are executed once again until the HSYNC request is 
made. If it is determined in Step S24 that the HSYNC request has been 
made, then the image data stored in the scan buffer in the form of a bit 
image is supplied to printer circuits 47 and 49 synchronously with 
predetermined timings (Step S25). As a result, laser system 17 starts 
forming an electrostatic latent image. Simultaneously, the flow of CPU 50 
returns to Step S1, and the above steps are once again executed until the 
transfer of the one-page image data is completed. The data transmission is 
continued until it is determined in Step S23 that data transfer is being 
performed and until it is determined in Step S26 that the transfer of 
one-page image data has been completed. After the transmission of the 
one-page image data, the flow returns to Step S1, and printer control 
section 48 is brought into the initial condition and thus becomes ready 
for the transfer of the image data corresponding to the next page. 
By repeating the above operation, an image corresponding to a plurality of 
pages is formed. 
As may be understood from the above, if paper sheet detector 26 detects 
paper sheet P fed from manual insertion tray 13, the supply of paper 
sheets P from paper sheet cassette 25 is suspended, so as to automatically 
convey paper sheet P from manual insertion tray 13 toward image transfer 
section 23. Therefore, it is not necessary to use operating panel 9 even 
when paper sheet P is manually inserted from manual insertion tray 13. 
Since, therefore, an image can be easily printed on the manually-inserted 
sheet, the apparatus can be easily handled. 
While image data is being transferred between host apparatus 58 and the 
image forming apparatus, the "DATA" lamp included in LED displays 9b 
continues to flicker, thereby informing the operator that the data 
transfer is being performed. Even if CPU 50 is used for a long time, the 
operator easily understands that the data transfer is being performed. 
Therefore, the apparatus of the present invention easily monitored for 
operability. 
The memory of IC card 65, 66 or 67 stores data of various kinds, such as 
font data, emulation data, image data, etc. The image data pertains to a 
normalized table, a chart, and a sentence, and image data of either one 
kind or a plurality of kinds is stored in one IC card. The operator 
inserts an IC card storing this image data into one of IC card-insertion 
ports 11, and then operates either the "NEXT ITEM" key or the "PRECEDING 
ITEM" key of the menu key until the message "LOAD CARD nm", is shown on 
the message display region on the left side of LCD display 9a (the message 
"LOAD CARD nm" is used for reading the m-th image information stored in 
the n-th IC card [65, 66, or 67]). In this condition, the operator 
operates either the "NEXT ITEM" key or the "PRECEDING ITEM" key of the 
value key until a message (e.g., "YES") for commanding the start of a read 
operation is displayed. In this fashion, the image data is transferred 
from the IC card to the image forming apparatus. 
A description will be given, with reference to the flow chart shown in FIG. 
10, as to how image data is transferred from an IC card to the image 
forming apparatus described above. 
First of all, a code stored in the ROM of the IC card is checked in Step 
R1, so as to confirm the inserted condition of the IC card. If the 
inserted condition of the IC card is confirmed in Step R1, then a check is 
made in Step R2 to see whether or not a data transfer request for 
transferring the data from the IC card to the image forming apparatus has 
been made. If the inserted condition of the IC card is not confirmed or if 
no data transfer request is made, the flow returns to Step S1. Let it be 
assumed that the inserted condition of the IC card is confirmed and that a 
data transfer request for requesting the transfer of the first data stored 
in the first IC card is made. In this case, a data type determination code 
stored in the ROM of the IC card is checked in Step R3. If the data is not 
image data, it is supplied to RAM S2 via internal bus 61 and is stored in 
RAM 52. Thereafter, the flow returns to Step 1. If the data is image data, 
a check is made in Step R5 to see whether or not the data having been 
transferred from IC card 65 is a command. If the data from IC card 65 is a 
command, then the operation corresponding to the command is executed in 
Step R6. If not, the flow advances to Step R7, skipping Step R6. In Step 
R7, a check is made to see whether or not the page buffer, provided in RAM 
52 as a data receiving buffer, is full. If this page buffer is not full, a 
check is made in Step R8 to see whether or not the data from IC card 65 is 
image data. If the data is not image data, the flow returns to Step S1, 
and the above-mentioned procedures are repeated until the end of the 
transfer of the data stored in the designated IC card. If, in Step R8, the 
data from IC card 65 is image data, Steps S7 through S26 mentioned above 
are executed. 
As mentioned above, the image forming apparatus of the present invention 
can form an image stored in an IC card, without depending on any of the 
host apparatuses. 
IC cards 65-67 used in the image forming apparatus of the present invention 
are colored in accordance with the memory types and with the contents 
stored therein. Therefore, the IC cards can be used without confusion. 
As mentioned above, the image forming apparatus provided by the present 
invention enables the priority orders of the host apparatuses to be easily 
altered and further enables a particular host apparatus to be selected for 
temporary priority use. 
It should become obvious to those skilled in the art that this invention is 
not limited to the preferred embodiments shown and described.