Method and apparatus for controlling data communication in a copying system

A method and apparatus for controlling data communication in a copying system which is provided with a copying machine and a plurality of peripheral units cooperating with the copying machine. The copying machine has a single serial transmitting port. Data from the copying machine is first transmitted to one of the peripheral units through the serial transmitting port. Then, a connection between the serial transmitting port and the one of the peripheral units is electrically switched to a connection between the serial transmitting port and the other of the peripheral units. Thereafter, data from the copying machine is transmitted to the other of the peripheral units through the same serial transmitting port.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and apparatus for controlling 
data communication in a copying system. 
Recent copying machines must speedily and exactly handle a large number of 
and various types of documents. To meet such requirements, the copying 
machine is systematized. For example, it is used in combination of 
peripheral machines, such as an automatic document feeder (ADF) and 
sorters. 
In such a systematized copying machine (referred to as a copying system), 
the copying machine contains a host CPU, and the peripheral machines also 
contain slave CPUs. The slave CPUs are under control of the host CPU via 
an interface. For the data communication among those CPUs, the copying 
machine is provided with a plurality of serial ports to respectively be 
coupled with the ADF and sorters. Also each of the sorters has a plurality 
of serial ports to be coupled with the copying machine and the other 
sorters. Use of the plurality of serial ports is uneconomical and will 
increase the cost to manufacture. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide data 
communication method and apparatus for a copying system having a copying 
machine and peripheral units, in which the data communication between the 
copying machine and the peripheral units and between the peripheral units 
is performed by using a single serial port of the copying machine and by 
using single serial ports of the peripheral units. 
According to one aspect of the present invention, there is provided a 
method of controlling data communication in a copying system which is 
provided with a copying machine and a plurality of peripheral units 
cooperating with the copying machine, the copying machine having a single 
serial transmitting port, the method comprising the steps of transmitting 
data from the copying machine to one of the peripheral units through the 
serial transmitting port, electrically switching a connection between the 
serial transmitting port and the one of the peripheral units to a 
connection between the serial transmitting port and the other of the 
peripheral units, and transmitting data from the copying machine to the 
other of the peripheral units through the serial transmitting port. 
According to another aspect of the present invention, there is provided a 
method of controlling data communication in a copying system which is 
provided with a copying machine and a plurality of peripheral units 
cooperating with the copying machine, the copying machine having a single 
serial receiving port, the method comprising the steps of receiving data 
from one of the peripheral units through the serial receiving port, 
electrically switching a connection between the serial receiving port and 
the one of the peripheral units to a connection between the serial 
receiving port and the other of the peripheral units, and receiving data 
from the other of the peripheral units through the serial receiving port. 
According to yet another aspect of the present invention, there is provided 
a method of controlling data communication in a copying system which is 
provided with a copying machine and a plurality of peripheral units 
cooperating with the copying machine, the copying machine having a single 
serial transmitting port and a single serial receiving port, the method 
comprising the steps of transmitting data from the copying machine to one 
of the peripheral units through the serial transmitting port, receiving 
data from one of the peripheral units through the serial receiving port, 
electrically switching a connection between the serial transmitting port 
and the one of the peripheral units to a connection between the serial 
transmitting port and the other of the peripheral units, and switching a 
connection between the serial receiving port and the one of the peripheral 
units to a connection between the serial receiving port and the other of 
the peripheral units, transmitting data from the copying machine to the 
other of the peripheral units through the serial transmitting port, and 
receiving data from the other of the peripheral units through the serial 
receiving port. 
Additionally, there are provided apparatuses for executing the 
above-mentioned methods for controlling data communication in a copying 
system. 
With such arrangements, the serial data communication between the copying 
machine and the sorter is performed by using a single serial port of the 
copying machine and alternately in a time divisional manner. The use of 
the single serial port of the interface of the copying machine leads may 
provide an inexpensive serial interface arrangement, and consequently 
leads to reduction of cost to manufacture. 
In the copying system, when a plurality of the sorters are used, a first 
sorter is coupled with the copying machine, and is coupled with the 
remaining sorters. The data communication among the plurality of sorters 
are performed during the data communication between the copying machine 
and the first sorter. The interface of each sorter accepts only the data 
necessary for the sorter per se. 
Accordingly, an effective data communication is realized in the copying 
system, and by using the interfaces each having a single serial port. 
Other objects, features, and advantages of the present invention will be 
apparent from the following detailed description of the preferred 
embodiment as illustrated in the accompanying drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of a copying system according to the present 
invention will be described with reference to the accompanying drawings. 
An overall configuration of a copying system which is an embodiment of the 
present invention is schematically illustrated in FIG. 1. The copying 
system is constituted by a copying machine 10, an automatic document 
feeder (ADF) 20, and three sorters 30a, 30b and 30c. The copying machine 
10 contains image forming process members 11 such as a belt like 
photosensitive member. The ADF 20 is placed on the top of the copying 
machine 10. The ADF 20 automatically feeds a set of originals such as 
documents to be copied to a document table 21 in the top surface of the 
copying machine. On the exit side of the copying machine 10, the three 
sorters 30a to 30c are located side by side. In this instance, three 
sorters are used, but if required, it may be larger or smaller than three. 
The first to third sorters 30a to 30c are provided with bin rows 31a to 
31c, respectively, for receiving sorted copies, or copied papers, which 
are arrayed in parallel and slanting to the right (as viewed in the 
drawing). The first sorter 30a closest to the copying machine 10 uses a 
reversing unit 34 for reversing copies. 
As shown in FIG. 2, the copying machine 10, ADF 20, and sorters 30a to 30c 
contain serial interfaces 14, 22, 32a, 32b and 32c, respectively. Those 
interfaces are serially connected as shown, and have the same circuit 
arrangements. More detailed connection of these serial interfaces are as 
shown in FIG. 3. In the figure, reference character R indicates a 
receiving terminal and character T represents a transmitting terminal. 
A circuit arrangement of the interface 14 of the copying machine 10 is 
illustrated in FIG. 4. As shown, a central processing unit (CPU) 50 of the 
copying machine 10 contains a control port , a serial transmitting port 
TXD, and a serial receiving port RXD. A light emitting diode (LED) 53 for 
transmitting data TXD1 to the ADF 20 is provided and connected to the 
serial transmitting port TXD of the CPU 50, by way of an AND gate 51 and 
two inverters. Another LED 54 for transmitting data TXD2 to the first 
sorter 30a is also connected to the serial transmitting port TXD, by way 
of an AND gate 55 and two inverters. A photo transistor 58 for receiving 
data RXD1 from the ADF 20, is connected to the serial receiving port RXD, 
by way of a buffer, an AND gate 56, and a NOR gate 60. A photo transistor 
59 for receiving data RXD2 from the first sorter 30a is connected to the 
serial receiving port RXD, by way of a buffer, an AND gate 57, and the NOR 
gate 60. The port of the CPU 50 is connected through an inverter 52 to 
the first input port of the AND gate 50 that is contained in the data path 
from the serial port TXD of the CPU 50 to the LED 53 for the ADF 20, and 
also to the first input port of the AND gate 56 that is contained in the 
data path from the photo transistor 58 for the ADF 20 to the serial 
receiving port RXD of the CPU 50. 
For transmitting data from the copying machine 10 to the ADF 20, the CPU 50 
in the copying machine 10 containing the interface 14 thus arranged places 
a logical "L" level at its control port . The "L" level signal is 
inverted into an "H" level signal, which in turn is applied to the first 
input port of the AND gate 51. At this time, the CPU 50 transfers data 
TXD1 from the serial transmitting port TXD to the second input port of the 
AND gate 51 via the inverter. Under this condition, the AND gate 51 is 
enabled to allow the data signal to pass to the LED 53. The data signal 
reaches the LED 53 and energizes the LED 53, so that the data TXD1 is 
transferred to the interface 22 of the ADF 20. During this communication 
from the copying machine 10 to the ADF 20, the "L" level signal from the 
control port is directly applied to the AND gate 55, and the gate 55 
remains disabled Therefore, the data from the serial transmitting port TXD 
will never go to the LED 54 to be coupled with the first sorter 32a. 
To receive data from the ADF 20, the CPU 50 sets the port at an "L" 
level The "L" level signal is inverted by the inverter 52 and applied to 
the first input port of the AND gate 56. At this time, data RXD1 comes 
through the photo transistor 58 from the ADF 20 and reaches the other 
input port of the AND gate 56. At this time, the gate 56 is conditioned to 
allow the data RXD1 to pass therethrough and to reach the serial port RXD 
of the CPU 50. Also during this communication, the AND gate 57 is disabled 
by the "L" signal from the control port , and prohibits the data RXD2 
of the first sorter 30a coming through the photo transistor 59 from 
entering into the serial receiving port RXD of the CPU 50. 
The data transmission between the copying machine 10 and the first sorter 
30a will be described. As seen from FIG. 5, after receiving the data RXD1, 
the ADF 20 returns the data RXD1 to the copying machine 10 within a 
predetermined period. After receiving the data, the copying machine 10 
switches the signal level at the control port from an "L" level to a 
"H" level. When an "L" level is set at the port , the AND gate 51 is 
disabled, while the AND gate 55 is enabled. The data TXD2 outputted from 
the serial transmitting port TXD of the CPU 50 goes through the AND gate 
55 and the inverter, and reaches and energizes the LED 54 to be coupled 
with the first sorter 30a. With the energization of the LED, the data TXD2 
is transmitted to the first sorter 30a. When receiving the data RXD2 from 
the sorter 30a, the data received by the photo transistor 59 is applied to 
the AND gate 57. At this time, the gate 57 has received a "H" level signal 
from the port and is enabled to allow the data to pass there and reach 
the serial receiving port RXD of the CPU 50. 
The circuit arrangement and the operations of the interface 14 of the 
copying machine 10 for receiving and transmitting the data to and from the 
ADF 20 and the first sorter 30a are substantially the same as the 
interfaces 32a, 32b and 33c of the sorters 30a, 30b and 30c. 
As seen from in FIG. 5, the copying machine 10 first transmits data to the 
ADF 20. After receiving the data, the ADF 20 transmits data to the copying 
machine 10. In other words, the ADF 20 responds to the data from the 
copying machine 10, and returns the data thereof to the copying machine 
10. 
Subsequently, the copying machine 10 transmits data to the sorter. The 
transmitted data contains data of paper size, on/off of motors of the 
sorters, bin addresses, and the like. After receiving the data from the 
copying machine, the sorter returns data to the copying machine. The data 
transmitted from the sorter contains data indicating if a copy or copies 
are contained in a bin or bins (of each block, if bins are arranged in 
blocks) in the sorter, data indicating bin address in which copies just 
transported have been put, and the like. In this way, the copying machine 
10 transfers data to and from the ADF 20 and the sorters 30a to 30c, 
alternately and time divisionally. 
Switching the connection of the copying machine 10 to the ADF 20 over to 
the connection of the copying machine to the sorter and vice versa may be 
realized by using a timer, for example. Specifically, at the time of 
starting the data transmission to the ADF 20, the timer starts its 
operation. The timer disconnects the machine to ADF connection and 
connects the machine to sorter connection, after a time slight longer than 
the time required for data transmission and reception. Also at the time of 
starting the data transmission from the first sorter 30a to the copying 
machine 10, a timer starts its operation. The timer disconnects the sorter 
to machine connection and connects the sorter to sorter connection, after 
a predetermined time. In this instance, the data used in the copying 
system are all coded data. 
When considering a data transmission speed, the time divisional data 
communication by a single serial port is inferior to the conventional data 
communication by using individual ports. Practically, the inferiority of 
the data communication by the control system according to the present 
invention is negligible. For example, let us consider a case that data 
each having a 11-bit data length consisting of data of 8 bits, start bit 
of 1 bit, stop bit of 1 bit, and parity bit of 1 bit, are transmitted at 
4800 bit/sec. In this case, approximately 4.6 msec is taken for the data 
transmission and reception to and from the ADF 20. If the timer switching 
time is set at 5 msec, the data from the ADF 20 is obtained every 10 msec. 
In the ADF 20 and the sorters, however, there little occurs a case that 
they have such data that must be processed within several tens msec. 
The data transmission among the first to third sorters 30a to 30c are 
performed during the data transmission between the copying machine 10 and 
the ADF 20. During this period, data transmission will never be performed 
between the copying machine 10 and the sorters. 
In this way, the copying machine 10 can perform the data communication with 
the ADF 20, and the sorters 30a to 30c, through the single serial ports 
RXD and TXD. 
The data communication among the sorters 30a to 30c will be described. 
The data transferred from the copying machine 10 to the sorter side 
contains mainly bin address data for sorting and distributing copies into 
related bins in the sorters. Additionally, it contains on/off data for 
turning on and off the motors, copy size data, and the like. In the 
copying system shown in FIG. 1, the bin rows 31a to 31c in the sorters 30a 
to 30c contain 20 bins, respectively. A total of 60 bins are used in this 
copying system. Let us consider a case that 50 copies are produced, and 
these copies must be sorted and put into the bin rows 31a to 31c of the 
sorters. In this case, the bin rows 31a and 31b of the first and second 
sorters 30a and 30b are completely filled with the copies of 40. The 
remaining 10 copies are put into 10 bins of the bin row 31c of the third 
sorter 30c. 
The data communication among the sorters 30a to 30c, and between the 
copying machine 10 and the first sorter 30a will be described with 
reference to FIG. 6 describing a sorter serial communication. Bear in mind 
that the serial interfaces 32a to 32c of the sorters 30a to 30c have the 
same circuit arrangements as already mentioned. Where the flow of the 
copies derived from the copying machine 10 is involved, the copying 
machine 10 is located upstream of the first sorter 32a, and the second 
sorter 32b is located downstream of the first sorter 32a. For the second 
sorter 32b, the first sorter 32a is located upstream of it, and the third 
sorter 32c is located downstream of it. For the third sorter 32b, the 
second sorter 32b is located upstream of it. 
When one sorter, for example, the first sorter 30a receives data from its 
upstream side, the received data is stored in SIDTS of a reception buffer 
61. In practice, before storing in the reception buffer 61, some 
operation, described in detail later, is carried out. When the data comes 
from the downstream side, it is stored in SIDTM of a reception buffer 62. 
The upstream or downstream can be discriminated by a logical state, "H" or 
"L", at a control port of a CPU 33a (FIG. 4) of the sorter 30a. 
To be more specific, when the copying machine 10 transmits data to the 
first sorter 30a, the first sorter 30a loads the received data into the 
SIDTS of the buffer 61. The CPU 33a in the serial interface 32a determines 
whether or not the data received and stored in the SIDTS of the reception 
buffer 61 concerns the first sorter 30a. If the answer is "YES", or it 
concerns the first sorter, the data is subjected to an appropriate 
internal processing in a block 63. If the answer is "NO", the data is 
loaded into SIDTSn of a data buffer 64. Here, the data indicating if the 
received data concerns the first sorter 30a or another sorter relates 
mainly to sorter bins. Let us consider a case, for example, that to put 
copies into a 35th bin, the copying machine 10 transmits data to the first 
sorter 30a. In this case, the fist sorter 30a needs the bin address data 
of 1st to 20th bin, bins, but does not need the data of the 35th bin. 
Accordingly, the data of the 35th bin is stored into the SIDTSn of the 
data buffer 64 so as to send the data to the second sorter 30b. Then, 
status data of the first sorter 30a and the data from the downstream 
sorter are set in SIDTM1 of a transmission buffer 65, and is transmitted 
to the copying machine 10. After the data transmission to the upstream 
side is completed (it is terminated after a preset time lapses from a 
transmission start), the data stored in the SIDTS1 of the transmission 
buffer 66 is transmitted to the downstream side. 
The data in the SIDTS1 of the transmission buffer 66, after it is 
transmitted, is temporarily stored into SIDTSn of the data buffer 64. In 
the data buffer 64, the data of the SIDTSn is successively stored into the 
SIDTS(n-1). When an data error occurs during the transmission or reception 
of the data, and the present sorter receives a request of a retransmission 
of the transmitted data, the data stored in the data buffer SIDTS0 is 
transmitted. In other words, for searching the data to be retransmitted, 
it is not necessary to go upstream beyond the data buffer SIDTSS0 in the 
present serial interface. When no data to be transmitted to the downstream 
side is stored in the data buffer, dummy data is transmitted to maintain a 
synchronism of the system operation. 
After transmitting the data in the SIDTS1 of the transmission buffer 66 to 
the downstream side, the present serial interface receives the data from 
the downstream side within a predetermined time. The received data is 
temporarily stored in the SIDTM of the reception buffer 62, and then is 
stored into the SIDTMn of the data buffer 67. Part of the data stored 
therein is subjected to an appropriate internal processing in a block 68. 
In the event that a jamming or any other trouble occurs in the second 
sorter 30b, the internal processing results in prohibiting the copies from 
being transferred to the second sorter 30b. Most of the data stored in the 
data buffer 67 are data to be sent to the upstream. The transmission of 
the data to the upstream is timed after the present interface receives the 
data from the upstream. 
Thus, in transferring data among the sorters 30a to 30c, each sorter 
fetches only the data that is necessary for the sorter per se, while the 
other data than the necessary data merely pass through the interface of 
that sorter. This is very convenient for the control of the sorters 30a to 
30c. The reason for this follows. In case that the copy machine 10 
produces the address data of the 35th bin, for example, the first sorter 
30a having 1st to 20th bins passes the 35th bin address data to the second 
sorter 30b. The the sorter 30b receives the 35th bin address data, and 
recognizes the address data concerning the sorter itself because it has 
the 21st to 40th bin addresses. In turn, it executes the processing of 
subtraction 35-20=15. On the basis of the subtraction result, the second 
sorter 30b controls its mechanism relating to a copy flow control so that 
the copy is put into the 15th bin as counted from the top as viewed in the 
flow of copies. Thus, the second sorter 32b subtracts the number of bins 
contained therein from the bin address, and uses the subtraction data as 
its bin address. After the subtraction is performed, viz., in this 
instance the address of the 15th bin is obtained, the control to be 
performed by the second sorter 30b is the same as that by the first sorter 
30a. This indicates that the same control software is applicable for all 
the sorters 30a to 30c. In other words, the software must discriminate 
those sorters 30a to 30c one from the others, but the same random access 
memory (ROM) or hardware may be used for those different sorters 30a to 
30c. 
The above feature implies that the first to third sorters 30a to 30c may be 
treated as the same type of sorters in the stages of manufacturing and 
sales. This is very useful in inventory management and cost to 
manufacture. Incidentally, in conventional copying systems, the second 
sorter and subsequent sorters are controlled by the first sorter, and 
therefore a hardware arrangement of the first sorter is different from 
those of the remaining sorters. For the discrimination of those sorters, 
it can be used to check at the time of power on, as to if the reversing 
unit 34 is present in the sorter under the discrimination. Additionally, a 
transmission from the first sorter 30a may make the discrimination. 
Furthermore, manually setting switches may be used, such as DIP switches, 
for the discrimination in such a way that the switch for the first sorter 
30a is set in on state, while the switches for the remaining sorters are 
set in off state. 
Turning now to FIGS. 7a through 7c, 8 and 9, there are shown flowcharts of 
subroutine programs for controlling the transmission and reception of data 
through the serial ports TXD and RXD in one of the sorters, for example, 
the first sorter. 
When a sorter receives data from the machine located upstream or downstream 
of the sorter, a main program is interrupted, and a subroutine program 
SB301 is executed as shown in FIGS. 7a through 7c. In this case, if the 
sorter receiving the data or under discussion is the first sorter 30a, for 
example, the upstream machine is the copying machine 20, and the 
downstream machine is the second sorter 30b. 
In the subroutine, to start, Step S1 is executed, to load the data RXDA 
that is received by the sorter via its serial ports RXD, into an 
accumulator Acc of the CPU of the sorter. In the next Step S2, control 
checks if a flag SLAVF is "1". This flag is used to indicate the data 
originating source from which the present received data comes, viz., the 
upstream machine or the downstream machine. If the source is the 
downstream machine, control advances to Step S3. If it is upstream, the 
CPU advances to STep S4 (FIG. 7b). Let us assume now that the data from 
the upstream machine is received. Then, control makes a parity check in 
Step S4. If a parity error is present, control goes to Step S18. In this 
step, retry-request data is loaded into the accumulator Acc and Step S14 
is executed to send the retry-request data to the upstream machine. FIG. 
10 shows a code map of 8-bit data that is transferred from the main 
controller (CPU 50) of the copying machine to the sorter. In the code map, 
the value in the horizontal line consists of the upper order bits of four, 
while the value in the vertical line, the lower order bits of four. As 
seen from the code map, the retry-request data is "FF". 
If no parity error is present, control reads the data RXDA out of the 
accumulator Acc in Step S5, and loads it into the SIDTS of the buffer 61. 
In the next Step S6, control checks whether or not the upstream sorter has 
requested a retry of the received data. In other words, the CPU checks 
whether or not the data in the SIDTS of the buffer 61 is "FF". If the 
answer is "YES", control proceeds to Step S19. In this step, the data of 
SIDTS0 previously transmitted to the downstream sorter that is stored in 
the data buffer 61, is stored into the accumulator Acc. Then, control goes 
to Step S14. If the answer is "NO", Step S7 is executed. 
In Step S7, control checks whether or not the data in the SIDTS of the 
buffer 61 is "AA", i.e., dummy data. If the answer is "YES", Step S13 is 
executed. If "NO", Step S8 is executed. In Step S8, control checks as to 
if a flag KOARSF is "1", viz., whether or not another sorter is present 
downstream of the sorter under discussion. If "YES", control goes to Step 
S9. In this step, a subroutine SB310 is executed and the data of the SIDTS 
of the buffer 61 into an empty storage location of the storage locations 
SIDTS1 to SIDTSn of the buffer 64. If "NO", control jumps to Step S10, 
because there is no need for storing the data into the data buffer 64 in 
preparation for transferring the data to the downstream sorter. In Step 
S10, control checks if the data in the SIDTS of the buffer 61 is "3C" 
(=60) or less, viz., the data is the bin address data. As seen from FIG. 
10, the bin address is assigned to "01" to "3C2." 
If the data is not the bin address data, a program of FIG. 7c is executed. 
If the bin address data, control goes to Step S11, to execute a subroutine 
SB314. This subroutine checks as to whether or not the bin address in the 
SIDTS of the buffer 61 concerns the sorter under discussion. The details 
of the subroutine are illustrated in FIG. 8. In the figure, Step S20 is 
first executed to check if the sorter under discussion is the first 
sorter. If the answer is "YES", control returns to the flow of the 
subroutine SB310 and progresses to Step S12 in the subroutine SB310. If 
"NO", Step S21 is executed to check if the sorter is the second sorter. If 
the answer is "YES" in Step S21, Step S22 is executed to check whether or 
not the bin address in the SIDTS of the buffer 61 is larger than "20". If 
the answer is "YES", control returns to Step S12. If "NO", control 
advances to Step S13. If the answer is "NO" in step S21, control advances 
to Sep S23 to check whether or not the bin address in the SIDTS of the 
buffer 61 is larger than "40". If the answer is "YES", control returns to 
the main flow of the subroutine and goes to Step S12. If the answer is 
"NO", control skips and returns to the main flow of the subroutine, and 
proceeds to Step S13. In Step S12, a subroutine SB315 is executed. This 
subroutine stores the data in the SIDTS of the buffer 61 into an empty 
storage location of the storage locations ADSCUO to ADSCUA. 
In Step S13, a subroutine SB305 is for a preparatory processing for 
transmitting data to the upstream machine. In this subroutine, so long as 
the data to be transmitted is present in the data buffer 67, the contents 
in the SIDTM1 to SIDTMn are successively transferred to the SIDTM0 to 
SIDTMn-1. When the data to be transmitted is absent, dummy data "AA" is 
loaded into the accumulator Acc. In the next Step S14, the contents of the 
accumulator Acc is transferred as transmission data TXDA through the 
serial port TXD to the upstream machine. 
In Step S15, as in Step S8, control checks if the flag KOARSF is "1", viz., 
whether or not there is another sorter downstream of the present sorter. 
If the answer is "YES", control proceeds to Step S16. If it is "NO", 
control goes to Step S17. In Step S16, control starts a 2.4 msec-timer to 
indicate an instance that data is transmitted to the downstream machine, 
removes a timer interrupt mask processing, and sets a flag TIMSF 
indicating the start of the 2.4 msec-timer to "1", and then returns to the 
main flow of the subroutine. In Step S17, control executes a timer 
interrupt mask processing and then returns to the main flow. 
In Step S10, if the data is not the bin address data, control executes a 
program of FIG. 7c. In Step S10, control checks whether or not the data in 
the SIDTS of the buffer 61 is within "90" to "D4". The code map within 
this range is assigned to the other data than the bin address. 
Accordingly, only when the answer is "YES", control advances to Step S24, 
and recognizes the contents, or the received data, in the accumulator Acc. 
Relationships between the data codes of the received data and their 
meanings are listed in the following table. 
TABLE 
______________________________________ 
Code Meaning 
______________________________________ 
"90" Turn off the reversing unit 34 
(Step S26) 
"91" Turn on the reversing unit 34 
(Step S27) 
"A0" Turn off the paper feed motor in the 
sorter (Step S28) 
"A1" Turn on the paper feed motor in the 
sorter (Step S29) 
"A4" Reset the system (Step S30) 
"AA" Dummy data (Step S31) 
"C1" A3 size paper (Step S32) 
"C3" B4 size paper (Step S33) 
"C4" A4 size paper (Step S34) 
"C6" B5 size paper (Step S35) 
"D0" Double letter size paper (Step S36) 
"D1" Letter size paper (Step S37) 
"D4" legal letter size paper (Step S38) 
______________________________________ 
If control decides in Step S32 that the received data comes from the 
downstream machine, control goes to Step S3 of FIG. 7a as already 
mentioned. In this step, control executes a parity error check. If a 
parity error exists, control proceeds to Step S46, to set a flag RETRYF to 
request a retry. Then, it goes to Step S44. If no parity error exists, 
control executes Step S40 to store the contents RXDA of the accumulator 
Acc into the SIDTM of the buffer 67. In Step S41, control checks whether 
or not the downstream sorter has requested a retry of the received data, 
that is, whether or not the data in the STDTM of the buffer 67 is "FF". If 
the answer is "YES", control goes to Step S46. If the answer is "NO", 
control goes to Step S42. In Step S42, control checks whether or not the 
data in the SIDTM of the buffer 67 is "AA", that is, the data is the dummy 
data. If it is the dummy data, control proceeds to Step S44. If it is not 
the dummy data, control proceeds to Step S43. In Step S43, t subroutine 
SB320 is executed. The data in the SIDTM of the buffer 67 is stored in an 
empty storage location of the SIDTM1 to SIDTMn. 
In Step S44, the flag SLAVF is set to "1" and the control port is set 
to "0", to switch the serial ports TXD and RXD to the upstream machine. In 
the next Step S45, the control executes the timer interrupt mask 
processing, and returns to the main flow. 
After the transmission of data to the upstream machine is conditioned, and 
2.4 msec elapses, the timer interrupt occurs and a subroutine SB360 is 
executed. In Step S50, the timer interrupt is masked, and in Step S51, 
control checks if the flag KOARSF is "1", viz., whether or not there is 
another sorter downstream of the sorter under discussion, as in Steps S8 
and S15. If the answer is "YES", control goes to Step S52. If the answer 
is "NO", the control returns to the main flow, because no downstream 
sorter exists. In Step S52, control checks whether or not the flag TIMSF 
is "1", that is, the 2.4 msec timer has started. If "NO", control goes to 
Step S53 because the timer does not operate. If "YES", Step S54 is 
executed. In Step S54, the flag TIMSF is set to "0". In the next Step S55, 
the flag SLAVF is set to "0", and the control port is set to "21", to 
switch the serial ports TXD and RXD to the downstream side. In Step S56, 
control checks if the retry-request flag RETRYF is "1". 
When a retry request is present, control proceeds to Step S57, to set the 
flag RETRYF to "0", and reaches Step S58. In this step, stores the 
contents of the SIDTS0 of the data buffer 64, or the previously 
transmitted data, into the accumulator Acc, in order that in Step S60, the 
data will be transmitted again to the downstream machine. When no retry 
request is present, control goes to Step S59 where it executes the 
subroutine SB306 for a preparatory processing to transmit data to the 
downstream machine. So long as the data to be transmitted is present in 
the buffer 64, the contents in the SIDTS1 to SITDSn are carried to the 
SIDTS0 to SIDTSn-1 in successive order. When such data is absent, the 
dummy data "AA" is stored into the accumulator Acc. In Step S60, the 
contents of the accumulator Acc are transferred as transmission data TXDA 
to the downstream machine. Then, in Step S61, control starts the 4.8 
msec-timer to check whether or not there is a data transmission from the 
downstream machine within a predetermined period of time after data is 
transmitted to the downstream machine. Further, control remove the timer 
interrupt mask processing, and returns to the main flow. 
If the flag TIMSF is set to "0" in Step S52, control advances to Step S53 
because the data has been transmitted to the downstream machine, and sets 
the retry-request flag RETRYF to "1". In the next Step S62, the flag SLAVF 
is set to "21" and the control port is set to "20" to switch the 
serial ports TXD and RXD to the upstream side. Then, control returns to 
the main flow. 
FIG. 11 shows a code map of the 8-bit data transmitted from the sorter side 
to the main controller (CPU 50) of the copying machine. The value in the 
horizontal line consists of the upper order bits of four, while the value 
in the vertical line, the lower order bits of four. For example, "60" 
indicate that no paper is present in the 1st to 20th bins; "61", paper is 
present in the 1st to 20th bins; "70", the door of the sorter with the 1st 
to 20th bins is closed; "71", the door of the sorter with the 1st to 20th 
bins is open; "80", no jumming occurs in the sorter with the 1st to 20th 
bins; and "81", jumming occurs in the sorter with the 1st to 20th bins. 
While the description thus far given relates to the data 
transmission/reception by one sorter, for example, the first sorter, the 
main controller of the copying machine may also carry out the transmission 
and reception of data to and from the adjacent machine by using the serial 
ports TXD and RXD in a similar way. 
Many widely different embodiments of the present invention may be 
constructed without departing from the spirit and scope of the present 
invention. It should be understood that the present invention is not 
limited to the specific embodiments described in this specification, 
except as defined in the appended claims.