JP2001016297A - Serial communication equipment, serial communication method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To self-diagnose that a communication request signal from a slave station is normally in operation while maintaining the reliability of serial communication between a master station and the slave station. SOLUTION: In the serial communication method, when communication frequency between a master station and each slave station is less, e.g. in a standby state for an operating state of an electronic photographing device adopting this serial communication system, fault discrimination processing of a communication request signal from a slave station in steps S5-S12 is conducted in addition to the substantial serial communication and when the operating state has many communication frequencies between the master station and each slave station e.g. during a print state, this fault discrimination processing is skipped and only the substantial serial communication is exclusively conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a serial communication device, a serial communication method, and a storage medium for serially communicating information between a central processing unit and a plurality of electric units provided in an electronic device.

[0002]

2. Description of the Related Art A serial communication device for serially communicating information between a central processing unit and a plurality of electric units provided in an electronic device has been known.

[0003] Such a serial communication device includes a main device for serial communication called a master station of a central processing unit in the electronic device, and a slave station of a plurality of electric units scattered in the electronic device. The main device and the sub-device exchange information between the main device and the sub-device. Many electronic devices are used for the purpose of suppressing the ease of assembling electronic devices and manufacturing costs. Used in equipment.

Information exchange by a serial communication device has been basically performed by serial communication executed in response to an information exchange request generated by a main station attached to a CPU serving as a central processing unit. Therefore, when the slave station wants to exchange information, it transmits a communication request signal to the master station, and when the master station receives this signal, the master station executes serial communication in response to the signal, thereby receiving a signal from the slave station. Information was updated and both parties exchanged information. This exchange of information
Since the master station and the slave station are implemented on a one-to-one basis, the transfer information generated from the master station is transferred to a specific slave station, and the transfer information returned from the slave station is the master station. Both the master and slave stations had to be aware that they came from the slave station identified by

For this reason, many conventional serial communication devices have attached transfer information with identifier information designating a slave station. Therefore, in this transfer method, it is necessary to distinguish all the slave stations connectable to the transmission line by the identifier information, so that the method is established after limiting the maximum number of slave stations. In other words, the data length (number of bits) of the data (transfer information + identifier information) transferred to the slave station is determined according to the maximum number of slave stations that can exist on the transmission path. This means that communication protocols and data processing devices cannot be designed.

As described above, in the conventional serial communication device, it is necessary to determine the number of connectable slave stations in advance.
The number of slave stations must be set larger than actually required, and the communication protocol and the data processing device must be designed. This has increased the cost for manufacturing a serial communication device.

Further, when the configuration of the number of slave stations in the electronic equipment is changed and the design is changed accordingly, the data length of the basic transfer data is changed. I needed to.

In recent years, therefore, the data length (the number of transfer information bits + the number of identifier information bits) of the data (the transfer information + identifier information) transferred to one slave station has been fixed.
2. Description of the Related Art A serial communication device including a communication protocol that enables connection of a semi-infinite number of slave stations and a data processing device that performs data processing based on the communication protocol has been developed. As a result, the same serial communication device can be used with an optimum number of slave stations regardless of the number of slave stations provided in the electronic device, so that it is possible to easily cope with a design change in the middle, and The manufacturing cost can be reduced as compared with the conventional serial communication device.

Hereinafter, a serial communication device which can connect a semi-infinite number of slave stations while keeping the number of transfer information bits and the number of identifier information bits fixed will be described in detail with reference to FIGS. Before that, an outline of this serial communication device will be described.

In this serial communication apparatus, the master station creates transfer information of a predetermined data length, and the shift register circuit of each slave station (the number of constituent bits is, for example, 4 bits for convenience of explanation. The number of bits is not limited to this.) The slave station parallel output information from the master station is shift-transferred together with the transfer clock, and should be returned to the shift register circuit in advance to the shift register circuit before the shift transfer by the master station. By loading the parallel input information of the slave stations, information is exchanged between the master station and each slave station in the shift transfer performed by the master station.

Each slave station has a phase control counter circuit, and is configured to execute an operation specified by the count value of the phase control counter circuit. By controlling the count value of the phase control counter, the master station can control the operation of the slave station with respect to, for example, a shift register circuit. In order to control the phase control counter circuit of each slave station, the master station also includes a phase control counter, and by performing operation control in the same manner as the phase control counter circuit of the slave station,
The operation status of each slave station can be grasped by its count value, and the operation control of each slave station in the transmission path is executed to perform serial communication.

On the other hand, the master station recognizes a semi-infinite number of slave stations that can be connected to the transmission line with a fixed number of identifier information bits, and implements one-to-one information exchange in order to perform two-to-one information exchange. It is configured to perform communication independently.

One is communication for the purpose of recognizing a slave station existing on a transmission line, and is called "initialization communication" in the present serial communication device. In this initialization communication, identifier information of each slave station is received, and the sequence of slave stations in the transmission path is recognized based on the identifier information.

The other is communication for creating and transferring shift transfer data in accordance with the sequence of slave stations recognized in the initialization communication, and is called "normal communication" in the present serial communication device. In this normal communication, information exchange with each slave station is performed on a one-to-one basis. In other words, the sequence of the slave stations connected to the current transmission path is invariable once recognized by the initialization communication, so if the master station shifts and transfers data created according to the slave station order to each slave station, Similarly, from each slave station, return information data created in accordance with the order of arrangement of the slave stations is shifted and returned, so that information exchange is easily performed.

Here, a basic idea for recognizing the number of slave stations equal to or greater than the number of slave stations that can be represented by a fixed number of bits of identifier information will be described. Note that the fixed number of identifier information bits will be described as, for example, 4 bits, but this is for convenience of description and is not particularly limited.

First, as a premise, a slave station is classified into two types based on the configuration of electronic equipment to which the present serial communication device is applied.

One is that a slave station used as an indispensable unit for the operation of the electronic device main body is called a “main unit”, and identifier information is assigned by a fixed value code.

The other is a slave station which is not essential to the operation of the electronic device itself and is used as an option as a so-called extension unit, which is called an "option unit".
In each case, identifier information is allocated with the remaining codes after the fixed value code is allocated. That is, the identifier information of the option unit is all zero (0000B), all ones
(1111B), a fixed value for the main unit (for example,
Code value other than 1 (set to 1101B)
1B). Here, "B" is a symbol indicating that the preceding numerical value is a binary number (binary).

When the arrangement order of the transmission lines is considered only by the configuration of the main unit, the arrangement order is invariable since the main unit is an essential unit. That is, the set slave station arrangement for the main unit is
Since there is no change when arranged only in the main unit, a memory map may be formed according to the order of arrangement in the transmission path.

Next, an optional unit slave station that can be connected based on the main unit slave station order will be described.

When the slave station is an optional unit, it is not known whether the slave station is connected to the transmission line. Therefore, the identifier information is allocated in order, but the arrangement order is determined by the main unit unit arrangement. Using the units, a plurality of option units existing between the main units are grouped as one group, and in the same group, 1, 2, 3,... These groups are formed between different main units. That is, the identifier information to which the option unit is allocated may be duplicated as long as the group is different.

According to this method, even if the number of slave stations is half-infinite, it can be distinguished by 4-bit identifier information. More specifically, a maximum of 13 optional units can be allocated between the first and second main units (to exclude all 0s, all 1s, and fixed value codes of the main units) with non-overlapping code values. If there are five units, for example, 4 × 13 = 52 optional units can be identified on a one-to-one basis. Conversely, if a main unit including a dummy corresponding to the required number of optional units is prepared, a semi-infinite number of slave stations can be recognized within the allowable range of the electric transmission capacity of the transmission line.

The overall operation in the case where the present serial communication device capable of connecting a semi-infinite number of slave stations described above actually executes communication is as follows.

First, in the electronic equipment to which the present serial communication device is applied, the master station presets the number of all slave stations connectable to the serial communication transmission line and the arrangement order thereof, and stores the slave station parallel input / output information contents. Mapping to a memory provided on the master station side.

Next, the master station executes the initialization communication to receive the identifier information in accordance with the arrangement order of the slave stations connected to the actual transmission line, and to determine whether or not there is a slave station registered in the memory. Is set, the mapped slave station arrangement order is reset to the slave station arrangement order existing in the current transmission path. Thus, the master station can grasp the slave station arrangement order existing on the transmission path, and thereafter, constructs and outputs shift transfer data in accordance with the slave station arrangement order indicated by the reset memory map, and outputs the input shift transfer data. The serial communication is executed by storing the data in the memory according to the slave station arrangement order indicated by the reset memory map. The serial communication at this time is “normal communication”, and the normal communication occupies most of the serial communication.

As described above, the data of the number of information bits corresponding to the predetermined number of slave stations is prepared, the return data is loaded to each slave station, and then the shift operation is executed. Since each slave station can transfer information to the master station, the time required for communication is minimized.
Since the signal processing is further simplified and the circuit configuration of the slave station is simplified, the manufacturing cost is reduced.

Further, in the normal communication, after one cycle of the shift transfer for exchanging information, a second round of the shift transfer is performed again with the same information, and a single serial communication operation is performed. By performing the information exchange operation and comparing the information content of the first cycle with the information content of the second cycle, the accuracy of the information content can be improved with a simple configuration, and erroneous transmission of information can be prevented.

Next, a detailed configuration of the serial communication device will be described.

FIG. 7 is a block diagram showing a schematic configuration of an electronic apparatus to which the present serial communication apparatus is applied. The present electronic apparatus has one master station m and a plurality of (twelve in the illustrated example) slave stations s.
1 to s12. FIG. 7 illustrates all connectable slave stations, and an electronic device can be configured by a slave station arbitrarily selected from these slave stations.

FIG. 8 is a block diagram showing a detailed configuration of any one of the slave stations s1 to s12 in FIG. 7, and each of the slave stations s1 to s12 has the same configuration.

In FIG. 8, the input selector circuit 1 includes:
The parallel input information and the identifier input information are input, and the input selector circuit 1 selects either the parallel input information or the identifier input information as information to be returned from the slave station to the master station, and selects the input latch circuit 2 and the exclusive input information. The logical OR circuit A (hereinafter, referred to as “EXOR circuit A”) 3. The input latch circuit 2 latches and holds the selected information for the execution period of one serial communication, and holds the EXOR circuit A
3 and the shift register circuit 4.

The EXOR circuit A3 includes input information to the input latch circuit 2 (output information from the input selector circuit 1),
The output information from the input latch circuit 2 is compared for each bit, and the result is collectively output as one signal by a multi-input gate. This signal is turned on when any one bit changes. "1"), and at other times, it is turned off ("0") and output to the decode circuit B12.

The shift register circuit 4 is for the slave station to execute shift transfer. The shift register circuit 4 reads a shift-in signal in synchronization with a transfer clock and outputs information already stored as a shift-out signal. Further, the shift register circuit 4 reads the stored information twice and outputs the information to the latch circuit 5 and the EXOR circuit B6.

The double read latch circuit 5 latches and holds the information of the first cycle of the shift transfer, and outputs the information to the EXOR circuit B 6 and the output latch circuit 7.

The EXOR circuit B6 compares the information content in the second shift transfer with the information content latched and held by the twice-read latch circuit 5 on a bit-by-bit basis, and compares the result with one multi-input gate. This signal is turned on ("1") when any one bit does not match, and turned off ("0") otherwise.
Output to the decode circuit B12.

The output latch circuit 7 performs a latch holding operation in response to the latch signal output from the decode circuit B12 with respect to the signal output from the EXOR circuit B6, and outputs the result to the outside as a parallel output of the slave station.

The gate circuit 8 is for instructing the input selector circuit 1 on the type of information to be selected. The gate circuit 8 uses the transfer clock and the soft reset signal as its input sources, and based on this, the selection instruction signal. Is output. Here, the soft reset signal is one of three types of signals (soft reset signal, forced reset signal, and count instruction signal) classified by the decoding circuit A9 based on a 2-bit slave station coded signal output by the master station. 1 signal.

The transfer clock is input to the shift register circuit 4, clock number counter circuit 10, and phase control counter circuit 11. Clock counter circuit 10
Counts this transfer clock and outputs a timing pulse for each predetermined value, and the phase control counter circuit 11
In response to the count instruction signal classified by the decode circuit A9, a count operation, a count stop holding operation, and the like are performed.

The master station also has a master station phase control counter circuit that operates in the same manner as the phase control counter circuit 11, and controls shift transfer.

The decoding circuit B12 uses the Q output, which is the count result of the phase control counter circuit 11, as an input source,
An operation instruction is issued to each circuit based on the control phase timing, and an input signal from each circuit is output to the master station as a return phase signal based on the control phase timing.

The operation of the shift register circuit 4 is basically controlled according to the count value of the phase control counter circuit 11 operated by the slave station coded signal output from the master station. In this way, the slave station is controlled by the master station. Specifically, the count value of the phase control counter circuit 11 (hereinafter simply referred to as “control count value”) is transferred by the phase control counter circuit 11 in accordance with a slave station instruction coded signal output by the master station. The count is performed by performing a count operation (operation such as count-up, stop, control count value reset, etc.) using the clock as a clock source. Then, the control count value is input to the next-stage decode circuit B12, and the decode circuit B12 directly outputs a timing instruction signal to a circuit that executes each slave station operation.

Hereinafter, the operation processing of the slave station will be described focusing on shift transfer.

When a soft reset is instructed by the slave station coded signal, the control counter value becomes 00H ("H").
Means that the value before that is hexadecimal
l)).
During the soft reset, the input information of the input selector circuit 1 is selected by utilizing the fact that the control count value does not change even when the transfer clock is received. The gate circuit 8 is configured to switch the selection instruction signal of the input selector circuit 1 depending on whether or not the transfer clock is received during the soft reset. Thus, the input selector circuit 1 selects either the parallel input or the identifier input and transmits the information to the input latch circuit 2. Thereafter, when the soft reset is released and a new transfer clock is received, the input latch circuit 2 latches and holds the input information,
The information is accessed to the shift-in parallel input of the shift register circuit 4.

On the other hand, a latch signal is supplied from the decode circuit B12 to the input latch circuit 2, and the EXOR circuit A3
Compares the latch input and output of the input latch circuit 2 bit by bit and collectively supplies one signal to the decode circuit B12 by the gate circuit. This signal is a source of a communication request signal generated by the slave station, and is transmitted from the return phase signal to the master station at a predetermined control count value (valid at the timing of 0EH in this serial communication device). Is done.

Next, when the master station continuously instructs the control count value to be 01H, the output information of the input latch circuit 2 is shift-loaded into the shift register circuit 4, and the shift transfer operation is performed as the transfer clock is received. Be started. From this time, the master station generates transfer data and a transfer clock of the number of bits corresponding to the number of slave stations in the transmission path grasped in the initialization communication processing described later, and at a desired timing by a slave station instruction coded signal. While manipulating the control count value, instruction control is performed so that the control count value becomes 06H at the shift end timing for making a round of shift transfer.

The slave station has a control count value of 06H.
Then, it is determined that the first round of the shift operation has been completed, and the decode circuit B12 outputs a latch pulse for latching and holding the shift data of the shift register circuit 4 to the twice-read latch circuit 5. On the other hand, the shift register circuit 4
When the control count value becomes 00H, the information of the input latch circuit 2 latched and held can be accessed. Since the information content latched and held by the input latch circuit 2 is not updated except when the control count value becomes 00H, the same information content as the immediately preceding information content is retained when the control count value is 06H. ing.

Then, the master station sets the control count value to 07H.
Then, the second round of the shift transfer is started. The shift register circuit 4 loads the shift data again at 07H and starts the shift operation. On the other hand, the master station also loads the same information content as that in the first shift transfer, and generates transfer data and a transfer clock having the number of bits corresponding to the number of slave stations on the transmission path. Then, the same operation as in the first cycle is executed, and the instruction control is performed so that the control count value becomes 0CH in accordance with the shift transfer end timing.

When the control count value reaches 0CH, the slave station determines that the second-cycle shift transfer has been completed, and the EXOR circuit B6 compares the output of the double-read latch circuit 5 holding the first-cycle data with the output of the second-time latch circuit 5. The output of the shift register circuit 4 in which the data of the cycle is stored is compared bit by bit. As a result, the EXOR circuit B6 outputs an OFF signal when all the contents match for each bit, and outputs an ON signal when any one bit does not match.

When the control count value becomes 0DH, the decode circuit B12 outputs a latch holding pulse to the output latch circuit 7 if the read results match each other, and outputs the read result twice. When there is a mismatch, the return phase signal is turned on without outputting the latch holding pulse to the output latch circuit 7. When the return phase signal is turned on at 0DH, the master station determines that the shift transfer has failed due to a communication error, and recognizes a communication error. In this case, as will be described later in the description of the master station, the control count value is returned to 00H by a soft reset signal, and the above serial communication is executed again as a serial communication retry. If an error occurs even after the retry communication is performed a predetermined number of times, the operation of the entire device is stopped as a serial communication failure, and the processing is terminated while maintaining a predetermined state such as a serviceman call.

On the other hand, if the shift transfer is successful at 0DH,
The transfer information to the slave station is output as a slave station parallel output, and the shift transfer operation ends. Accordingly, the master station reads and compares the input shift transfer data from the slave station twice in the same manner, and updates the information content in a predetermined memory when all the data match, while reading and comparing the data twice and finds that there is no mismatch. If there is only one bit, the retry communication is similarly performed after the soft reset.

When the master station also determines that the shift transfer has succeeded, it operates the control count value to 0EH.
This time, the state of the return phase signal is detected in order to determine the presence / absence of a slave communication request signal from each slave station. This state of 0EH is maintained until at least one slave station or master station issues a communication request. If there is a communication request, the control counter value is immediately set to 00H, and the serial communication is again executed. That is, the master station determines that the control counter value is 0DH.
The return phase signal at the time is used as a transfer error judgment,
The return phase signal at the time of 0EH is determined as a slave station communication request.

As described above, the return phase signal output is read by the master station while distinguishing its meaning according to the control count value. Therefore, the master station is configured as necessary so that it can be determined with various contents according to the control count value, and by devising the operation timing of the control count value, it is possible to classify the return signal having various meanings. .

On the other hand, when the control count value becomes 0EH, the slave station outputs the output state of the EXOR circuit A3 as a return phase signal by the decoding circuit B12. While this control count value is 0EH, the presence or absence of a slave communication request is transmitted.
As described above, with respect to the latch contents of the input latch circuit 2 for latching and holding the shift-transferred slave parallel input information,
As soon as even one bit of the current slave station parallel information content accessed to the input terminal of the input latch circuit 2 is updated, it is output as a slave station communication request for requesting the master station to perform information exchange. By this signal, the same operation as the bidirectional serial communication configuration can be originally obtained even in the unidirectional serial communication configuration from the master station.

Next, the control processing executed by the master station will be described in more detail with reference to FIGS.

FIG. 9 is a block diagram showing an example of an electronic apparatus constructed by omitting some slave stations installed as options from the electronic apparatus of FIG. The electric unit (slave station) referred to as an option here is not limited to an option installed by a user.
It also includes electrical units installed during factory assembly.

In FIG. 7, the master station executes control based on the slave station arrangement order allocated in the order shown in FIG. In addition, the slave station arrangement order of the basic transmission line is determined according to the configuration of the electronic device to be used. However, if the slave station arrangement order is changed due to a specification change or the like, the slave station arrangement order becomes the basic. Change the slave station order.

In FIGS. 7 and 9, a ring-shaped transmission line including the slave stations s1 to s12 is provided starting from the master station m.

FIGS. 10 and 11 are diagrams showing an example of a memory map used when the serial communication apparatus performs information exchange, and shows a memory map of a storage memory (not shown) provided only in the main station. It shows the transition of. That is, the slave station parallel output information (a) and the slave station parallel input information (b) in FIG. 10 are obtained by mapping the slave station arrangement order on the basic transmission line in FIG. (A) and the slave station parallel input information (b) map the current order of slave stations in the transmission path of FIG. 9 by initialization communication described later, and show a state in which the memory map is reset. Things.

Then, based on the arrangement order of the slave stations in the reset memory map of FIG. 11, information exchange with each slave station is executed by normal communication, and the data content is updated. On the other hand, an electronic device to which the present serial communication device is applied executes device control by reading and writing the present memory map.

In FIG. 11, the bits represented by "X" and "Z" indicate information contents updated with the execution of normal communication.

FIG. 12 is a flowchart showing a procedure of a serial communication process executed by the serial communication device.
FIG. 13 is a flowchart showing a detailed procedure of the initialization communication process in FIG. 14 and FIG.
13 is a flowchart showing a detailed procedure of a normal communication process in FIG.

In the case of normal communication, a so-called double feed and double reading mode is executed in which the shift transfer for executing the serial communication operation is performed twice and the information contents of the first and second rounds are compared. However, in the case of the initialization communication, the communication operation is controlled to be forcibly terminated by performing a soft reset at the stage where the shift transfer for executing the serial communication operation has been completed. This is because the reset of the memory map is finished as soon as possible, and the system can be shifted to the normal communication. With this process,
The entire electronic device can be started up as quickly as possible. Therefore, in the case of initialization communication, resetting of the memory map by shift transfer is rounded up by one round of shift transfer, and the process proceeds to the next normal communication as one serial communication.

Hereinafter, the control processing executed by the present serial communication device centering on the master station will be described in detail with reference to FIGS.

When the power is turned on and the CPU (not shown) is reset, the initialization setting processing of the memory (not shown) of the CPU is executed, and the memory portion of the main station is connected to the basic transmission line. When the arrangement order of all possible slave stations is mapped, the control program of the electronic device by the CPU operation is started, and at the same time, the serial communication processing (FIG. 12) which is the control processing of the master station is started. Before performing information exchange with each slave station, the master station performs communication to determine the sequence of slave stations existing in the current transmission path, that is, initialization communication, before performing communication called normal communication. . At this time, the memory state of the master station is a memory map shown in FIG.

When the serial communication process is started, first,
In step S101, the retry counter value is checked to determine whether the value is equal to or less than a predetermined value. At first, since the retry counter value is zero, the process proceeds to step S102.

In step S102, it is determined whether or not the memory map reset flag is set ("1").
If not set, the process proceeds to step S103,
The operation of resetting the memory map is executed in the initialization communication process.

In the initialization communication process shown in FIG.
In step S121, an idle transfer from one transfer clock, which is an operation for making the input selector circuit 1 of the slave station of FIG. 8 access the identifier information of the slave station, is executed. (If the idle transfer of the transfer clock is not performed, the input selector circuit 1 of the slave station accesses the information content of the slave station.) Next, in step S122, the memory map is used for resetting. The communication abnormality flag for registering the abnormality of the memory pointer and the communication result is initialized, and the execution of the initialization communication after step S123 is started.

In step S123, the memory pointer is incremented to 01H, and in step S124, the value obtained by adding the top address of the memory map of the slave array output information in which the slave array order is registered in advance: MTO and the memory pointer value It is determined whether or not the memory address indicated by matches the final value address: MTE in the memory map of the slave parallel output information in which the slave array order is registered in advance.

If they match in step S124, it means that the scanning of the memory map has been completed. Now, it is determined that they do not match, and the flow advances to step S125 to prepare for output of transfer data to be shifted and transferred.

In this initialization communication processing, the contents of all zeros are shift-transferred. However, the present invention is not limited to this, and shifts other than all zeros may be shift-transferred depending on the use of the serial communication device.

Next, in steps S126 to S128, 4-bit shift transfer is executed in accordance with the circuit configuration of the slave station. That is, 1-bit shift-out signal and 1-bit
The output transfer clock is output, and the clock counter is incremented (step S126), and a 1-bit shift-in signal is input (step S127).
It is determined whether or not the bit-wise shift transfer has been completed (step S128), and if not, the processes of steps S126 and S127 are repeated until the transfer is completed.

When the shift transfer of 4 bits is completed, the process shifts to step S129 to process the identifier information from the first slave station returned to the master station by the shift transfer. That is, the contents of the memory address indicated by the sum of the start value address: MTO and the memory pointer value of the memory map, which is the slave parallel output information of the base memory map, are accessed, and the upper 4 bits are accessed. . Then, the contents of the upper 4 bits are compared with the identifier information of the bit configuration of the 4-bit configuration when it is determined in step S128 that the input is completed (step S1).
30) If they match, it is determined that there is a slave whose identifier information is registered in the slave parallel output information of the basic memory map, and the process returns to step S123. Is determined. On the other hand, if they do not match, it is determined that there is no slave station of the identifier information registered in the slave station parallel output information of the basic memory map, and in step S131, the identifier information indicated by the upper four bits of the slave station is determined. The content is cleared to all zeros (00H) meaning "no slave station" and re-registered, and in the following step S132, the memory pointer is incremented and the registration located next to the slave parallel output information in the basic memory map is performed. The slave station of the identified identifier information is designated, and the process returns to the step S129 to determine the existence of the corresponding slave station. In other words, the memory area of the non-existing slave station is set to 00H to cancel the registration, and the existing memory area of the slave station retains the already registered identifier information, so that the current slave station arrangement order is reset. You.

By repeating the above processing and resetting the slave station arrangement order of the basic memory map, step S1
At 24, since the scan address reaches the address value MTE at which it is determined that the scan of the registered slave station should be terminated, the process moves to step S133, and the master station counts the total number of transfer clocks actually shifted and output during execution of the initialization communication. Divides the count value of the clock number counter provided by 4 bits, which is the number of bits constituting one slave station, to calculate the total number of slave stations present on the current transmission line, and determines the slave station determined to be present on the reset memory map. By comparing with the total number, self-diagnosis is performed to determine whether or not the slave station arrangement order reset by the initialization communication has been normally performed.

If it is determined in step S133 that they match,
It is determined that the reset has been normally performed, and the process proceeds to step S134. After the reset flag is set, the initialization communication process ends.

On the other hand, if there is a mismatch in step S133, it is determined that the reset is not normal, and the reset flag is reset, the process proceeds to step S135, the retry counter is incremented and the reset is performed once. The initialization communication processing ends.

Returning to FIG. 12, when the initialization communication processing is completed, the serial communication processing is temporarily terminated.

When the serial communication process is started again, the retry counter value is checked in step S101, and it is determined in step S102 whether the memory map has been reset. If so, the process proceeds to step S105, and the process proceeds to a normal communication execution operation described below. If the reset has failed, the process returns to step S103 to retry the initialization communication process.

If the initialization communication process succeeds even once, the process proceeds to normal communication after step S105. If the initialization communication process continues to fail, the retry counter value is incremented in step S135 in FIG. The count value exceeds a predetermined value, and step S in FIG.
At 101, it is determined that the communication cannot be performed, and step S104
Then, the communication failure processing is executed. In this communication failure process, the operation of the entire electronic device is stopped as a device failure, and a serviceman's response is required.

The master station control of the initialization communication has been described above. Here, a specific initialization communication operation will be briefly described based on the entire operation of the serial communication device with reference to FIGS.

The resetting of the memory map by the initialization serial communication is performed based on the basic memory map of the slave station arrangement order shown in FIG. First, the master station shifts and transfers the information contents of the lower 4-bit string of the slave station parallel output information of the memory map in the base station arrangement order to each slave station to initialize the slave station parallel output state.

In this serial communication apparatus, all zeros are set to initialize the slave station parallel state.
The present invention is not particularly limited to this, and the contents of the initialization information may be set in advance when a basic memory map in the slave station arrangement order is created.

Then, as described above, the master station outputs a soft reset signal to each slave station, and operates the transfer clock to shift the slave station identifier input contents to the shift register circuit 4.
To load. Thereafter, the slave parallel output information for initializing the slave parallel output state is shifted and transferred. As a result, the slave station parallel output information contents to be initialized are output to the parallel output terminals to the slave stations, and the identifier information contents are sequentially returned to the master station in the slave station arrangement order of the transmission path. The master station divides this identifier information content every 4 bits, and resets the current slave station sequence order of the transmission line while comparing it with the order of the identifier information content registered in the basic slave station sequence memory map.

Next, the rules for the identifier information will be briefly described.

In the identifier information, an electric unit required for the configuration of the electronic device is referred to as a main unit, a fixed value is allocated, and an electric unit capable of performing an operation without the configuration of the electronic device is referred to as an optional unit. And assign values in order. However, in the case of this optional unit, it is not simply allocated in order from 1. That is,
Since the main unit always exists in the apparatus, it is sufficient that the main unit can be confirmed to be at a position in the transmission line order set in advance. Therefore, the identifier information can be set with a fixed value. Since the optional units always exist between the main units whose position order has already been determined, the optional units are numbered sequentially based on one main unit. Therefore, the identifier information of the option unit has no duplicate identifier information content between one main unit, but it is allowed to be duplicated between different sets of main units, and the identification judgment can be made. . In FIG. 10, an example of the assignment of the identifier information is shown in the upper four bits of the slave station parallel output information.

Based on the definition of the identifier information according to such an agreement, the process of resetting the memory map will be described using the transmission line shown in FIG. 9 as an example. Note that this memory setting is performed in the same manner as a general CPU memory operation, and will be described below as an example, but is not particularly limited to this.

As means for operating the memory, there are a memory start position address (indicated by MTO in FIG. 10) and a memory pointer counter, and the contents of the memory indicated by the memory start position address are used as a reference counter. And
If the identifier information shifted and transferred is the main unit, the reference counter value of the memory content indicated by the head position address of the memory is incremented. If the identifier information is the optional unit, the memory pointer counter value is incremented.

First, checker identifier information (main unit) is shift-transferred to the master station. In this case, since the main unit is used, the reference counter value is incremented to 01H. On the other hand, the memory pointer counter value is not incremented and remains at 00H. Then, scanning is performed from the start position address of the base memory map, and an address position in which the identifier information content of the main unit located in the order indicated by the reference counter value is registered is determined from the base memory map ( In this case, since it is 01H, the checker which is the main body unit located first is calculated), and the reference counter address is set at that address position.

Next, the upper four bits of the memory at the address indicated by the result of adding the reference counter value and the memory pointer counter value
The bits are compared with the shift-transferred identifier information contents. In this case, the first main unit 0
The contents of the second memory (indicated as a checker in FIG. 10) match the contents of the identifier information of the transferred checker for comparison. If they match, it is determined that there is a corresponding slave station, and the upper 4
The bit is left as it is, and the state that there is a slave station is set.

Next, the sorter identifier information (option unit) is shifted and transferred. In this case, since this is an optional unit, the reference counter value is not incremented and remains at 01H, and the memory pointer counter value is incremented to 01H. As a result, the first memory (shown as a sorter in FIG. 10) after the first main unit is matched with the transferred sorter identifier information for comparison. Therefore, it is similarly processed that there is a slave station.

The identifier information to be shifted next is shown in FIG.
Higher pressure red (optional unit). In this case, since it is not the main unit, the memory pointer counter value is incremented to 02H. On the other hand, the reference counter value remains at 01H. Therefore, the memory located second after the main unit located first (switched back in FIG. 10) is compared with the transferred identifier information of the sorter. As a result, a mismatch occurs. First, the upper 4 bits of the switchback memory, which is the second memory located after the first main unit, are reset to all zeros, and there is no corresponding slave station.

Next, the value of the memory pointer counter is incremented again, and 03H is compared with the content located in the next memory map. That is, it is compared with the memory located third after the main unit located first. Similarly, in this case, it is determined that they do not match,
The non-matching memory is set as no slave station and the comparison is continued.

In this case, when the memory pointer counter value is 04H, that is, when the memory pointer counter value is compared with the fourth memory located after the first main unit, it is determined that the slave station of this memory is present. Set.

Next, as shown in FIG. 9, the identifier information (main unit) of the high voltage 1 is shifted and transferred. When the identifier information content of the main unit is received, first, starting from the memory indicated by the reference counter value and the memory pointer counter value, the optional counter of the optional unit registered between the main units indicated by the incremented value of the reference counter value is started. Set all memory contents to no slave station. In this case, high-pressure yellow (optional unit) corresponds to this. Next, based on the incremented reference counter value, the reset of the basic memory map is continued as described above. When the reference counter is incremented, the memory pointer counter value is cleared and returned to 00H.

By executing the above operation for all the basic memory maps, the resetting of the memory is performed as shown in FIG.
This is executed as shown in FIG. In other words, this memory operation is basically performed in the form of the optional unit located at the position after the main unit located at the position, and the memory contents are set.

Hereinafter, steps S105 to S11 in FIG.
The normal communication indicated by No. 2 will be described.

In the figure, when the above-described initialization communication processing is executed in step S103, a memory map reset flag is set. As a result, the memory map is shown in FIG.
As shown in the upper four bits of the slave station parallel output information in FIG. 7A, the slave station arrangement order in the basic memory map is reset to the slave station arrangement order of the slave stations existing on the current transmission path. Normal communication is executed based on the state of the slave station arrangement order.

When the process proceeds from step S102 to step S105, the retry flag is checked to determine whether or not there is retry communication. In the retry communication, similarly to the processing described in the initialization communication, when one serial communication fails, the retry counter is incremented, and when the count value is within a predetermined value, the retry communication is performed. And usually also exists in communication control.

Note that the configuration of the retry communication means uses the same means configuration since the initialization communication and the normal communication, which are the two types of communication means of the present serial communication device, do not proceed simultaneously. That is, when an error occurs in the retry communication exceeding a predetermined value, both the initialization communication and the normal communication shift from step S101 to step S104, and are processed in the communication failure processing routine. On the other hand, when executing the retry communication, in the case of the initialization communication, as described above, the retry counter is incremented in step S135 in FIG. 13 and the process proceeds to step S102 in FIG. 12 while the reset flag is reset. Then, the retry communication is executed because the reset flag is not set. In the case of normal communication, the retry flag is reset in step S112 after the normal communication is executed.
05, it is determined that retry communication is to be executed. That is, the retry communication control for the initialization communication and the normal communication is controlled separately, but the flags and counters necessary for the error processing routine and processing are shared.

When the resetting of the memory map is completed, it is determined in step S105 that there is no retry communication.
At 106 and S107, a request for execution of normal communication is awaited by either the request flag at the master station or the communication request signal at the slave station. When the initialization communication has been completed, since both the phase control counter 11 of the slave station and the control count value of the master station phase control counting means are set to 00H by the communication software reset, the slave station communication request signal in step S107 is set. Is invalid. Therefore, although not particularly shown, the master station sets the master station communication request flag immediately after finishing the initialization communication, and instructs execution of the normal communication in step S106. On the other hand, if the normal communication has been performed even once, the control count value is 0EH, and as described above, the system waits for the execution instruction of the normal communication. That is, the process proceeds from step S107 to step S112, resets the processing signals for retries and failures, temporarily ends the serial communication processing, and again executes steps S105 to S107.
And waits for the execution of the normal communication to detect the execution instruction. Then, when an instruction to execute normal communication is received, step S
The routine proceeds to 108, where normal communication processing is executed.

In the normal communication process shown in FIG. 14, first, in step S141, communication software reset is executed to synchronize the execution of communication.

Next, in step S142, a flag for executing communication and each counter value are reset.

In step S143, the memory pointer for memory operation is incremented. In steps S144 and S145, the control counter value is loaded and checked from the phase control counter of the main station, and is a predetermined value registered in advance. It is determined whether or not. In this case,
Two points are determined: 00H when the slave station input information to be shifted from the slave station is selected and 06H when the shift transfer is performed once. Further, the value of the double reading comparison result after performing the shift transfer twice is set to 0DH, and the determination is made in steps S160 and S161 in FIG. On the other hand, the validity period of the slave station communication request signal is set to 0EH. Here, although the timing determination is not particularly performed, the communication operation in the normal communication is terminated, and the next communication executable state is set to 0EH. It is controlled to be.

If it is determined in step S145 that the control counter value is the predetermined value (00H, 06H), the process proceeds to step S14.
6, the on-check of the return phase signal is performed. On the other hand, if the control counter value is not the predetermined value in step S145, the process proceeds to step S147 in FIG. 15, and the off-check of the return phase signal is performed.

Then, it is turned on when the return phase signal is checked on in step S146, or in step S14.
If it is off when the return phase signal is off-checked in step 7, it is determined that the phase timing is normally synchronized, and the routine goes to step S150 in FIG. On the other hand, when the return phase signal is turned on in step S146,
Alternatively, if the return phase signal is on at the time of off-check in step S147, it is determined that the phase timing is out of synchronization, and the phase error bit of the communication abnormality flag is set in step S148 in FIG.
Execute the communication software reset to cancel the normal communication currently being executed. In this case, it is determined in step S109 of FIG. 12 that there is an abnormality, and the process proceeds to step S110, where a communication abnormality flag analysis is performed, and the process proceeds to step S11.
In step 1, a retry flag is set to instruct retry communication, and the retry counter is incremented.

The execution of the communication error flag analysis routine is made up of a plurality of flags corresponding to various types of abnormal conditions, not shown. Then, when a flag indicating that the content of the abnormal state is light is set (the content of the abnormal state referred to here is one that has been identified and set in advance as a minor category and a severe category),
The retry counter value is incremented (+1) in the next step S111 to instruct execution of retry communication. On the other hand, when the flag indicating that the content of the abnormal state is heavy is set, the retry counter value is classified in advance so as to be directly set to a predetermined value causing an error on the spot. In this case, the retry communication is not executed according to the determination in step S101 after the serial communication processing is completed, and the process immediately proceeds from step S101 to step S104 to perform the communication operation in the communication failure processing routine. And the operation of the electronic device is stopped.

If it is determined in step S146 in FIG. 14 and step S147 in FIG. 15 that the state of the return phase signal is normal, the flow shifts to step S150 in FIG. 14 to start execution of normal communication.

First, it is determined whether or not the sum of the memory pointer value and the head address: MTO of the reset memory map indicated by the slave station parallel output information is the final address of the memory map: MTE. If they are equal, it means that one round of data to be shifted and transferred has been scanned, so the flow shifts to step S160 to enter post-processing after execution of normal communication. On the other hand, if they are not equal, that is, if the shift transfer is not completed, step S15
1 and S152, the upper 4 bits of the memory content indicated by the address of the sum of the memory pointer value and the start value address of the memory map: MTO are checked.

In step S152, the upper 4 bits are set to 00.
If it is H, it is determined that there is no registered slave station by resetting,
Returning to step S143 again, the memory pointer value is incremented, and the process shifts to execution of shift transfer in the next slave station in the memory map. Then, when it reaches step S152 again, it similarly checks the upper 4 bits of the memory contents. At this time, if the upper 4 bits are 00H, the same operation is repeated. If the upper 4 bits are not 00H, the lower 4 bits of the memory contents are accessed in step S153, and 1-bit shift for shift transfer is executed in step S154. . Further, in step S155, it is determined whether or not the clock number counter means of the master station has a predetermined value, and control of the control count values of the phase control counters of the master station and the slave stations is executed.

Then, in step S157, a 1-bit return signal by shift transfer is input, and in step S158, it is determined whether or not the shift transfer for 4 bits corresponding to one slave station has been completed. If it is not determined in step S158, the process returns to step S154 to repeat the same operation.
The process proceeds to 159, where the 4-bit data is stored in the slave-station parallel input information of the memory map shown in FIG. More specifically, the start value address of the memory map of the memory pointer value and the slave station parallel input information: MTI
Is stored in the lower 4 bits of the memory content indicated by the added value address to update the information content.

Then, in order to repeat the above operation to execute the shift transfer of the next slave station, step S14 is performed again.
Return to 3.

As described above, when it is determined in step S150 that the data scan of the slave station to be shifted and transferred has completed one cycle, the process proceeds to step S160 in FIG. 15, and the control count value of the phase control counter of the master station is set to 0DH
Then, the result of reading twice from each slave station is determined. If the return phase signal is on in step S161, it means that there is an error in the double reading comparison in any of the slave stations, and the process proceeds to step S163, where the double reading comparison error bit of the communication abnormality flag is set. Is set in step S1
At 64, a communication software reset for executing retry communication is executed. Thereafter, step S109 in FIG.
Then, as described above, the process proceeds from step S109 to step S110, where the execution request processing of the retry communication is performed.

On the other hand, if the return signal is not turned on in step S161, it means that there is no error in the double reading comparison in all the slave stations, so that step S1 is executed.
In step 62, the control count value of the phase control counter of the master station is set to 0EH, the communication request signal from each slave station is set to be valid, and it is assumed that the normal communication has been safely completed, and the process returns to step S109 in FIG. And the normal abnormality flag is 0
At 0H, the retry flag and the retry counter are reset in step S112 to complete one normal communication.
Thus, in the next communication execution, in steps S106 and S107, the communication standby state is continued until there is a communication request from the master station or the slave station, and communication is basically not performed unless there is a request.

The above is the master station control of the normal communication. This normal communication is performed after the arrangement order of the slave stations existing on the current transmission path can be reset by executing the initialization communication. When the arrangement order of the slave stations existing on the set transmission line changes, it is necessary to immediately execute the initialization communication to execute the resetting of the memory.

Although a part for generating a master station communication request is not particularly shown, the CPU controlling the electronic device main body sets a master station communication request flag for determining that each slave station needs to update information in each control task. Set to. Therefore, the master station checks the master station communication request flag in the part for controlling the normal communication of the serial communication processing (step S106 in FIG. 12) and determines whether or not the normal communication is to be performed.

As described above, the execution of the normal communication sequentially shifts and transfers the lower 4 bit information contents validated by the slave parallel output information of the reset memory map, and sequentially shifts the returned information contents to the slave station. Only the lower 4 bits of the parallel input information need be stored. That is, once the memory is reset, the master station can exchange information with each slave station by simple control such as simply transferring the contents of the memory. Furthermore, the time required to execute the normal communication can be processed in a minimum time because only the number of data bits for information exchange needs to be shifted and transferred.

[0116]

However, the conventional serial communication device has the following problems.

That is, the above-described conventional serial communication device performs unidirectional serial communication under the initiative of the master station, and when the information content is updated in any of the slave stations,
The slave station issues a communication request signal to the master station. Upon detecting this communication request signal, the master station executes serial communication regardless of the presence or absence of a master station communication request generated in the master station. As a result, the master station and each slave station can exchange information while always keeping the information contents up to date. One feature of the conventional serial communication device is that information is exchanged in this bidirectional serial communication mode. In other words, in the above-described conventional serial communication device, information exchange is established only after a communication request from a slave station occurs, and some abnormality occurs in a communication request signal from the slave station, and when the master station does not normally operate. Could not establish serial communication itself.

Therefore, in the above-described conventional serial communication device, when communication is performed by a communication request signal from a slave station, a change state of information content from the slave station before and after the execution of communication is determined, and a communication request signal from the slave station is received. In some cases, at least one bit of the information content from the slave station after the execution of the communication is determined to be updated, thereby performing a self-diagnosis that the communication request signal from the slave station is normally operating.

However, the conventional serial communication device described above
When the present invention is applied to an apparatus such as an electrophotographic apparatus, the communication execution frequency is very different between a print operation and a print standby (hereinafter simply referred to as “standby”). In the middle, many sensors connected to the parallel input terminal of each slave station repeatedly turn on and off sequentially at each phase, and the information content changes every moment, so that the communication execution operation is also followed one after another. If the self-diagnosis is performed each time a communication request signal is received from the slave station, the communication interval becomes longer.) However, there is a possibility that a change in input information of a certain sensor may be overlooked. Needless to say, if the information change of the sensor input is overlooked, the operation of the device itself will be hindered. A delay may occur and hinder the operation of the apparatus body.

This is a situation common to all equipment to which the above-mentioned conventional serial communication device is applied. If communication is frequently performed during a certain specific operation, the self-diagnosis executed during that time is not performed. The time required for one communication is lengthened, and the transmission of slave station information may be delayed, which may hinder the operation of the apparatus. Therefore, in some cases, the self-diagnosis may reduce the reliability of communication.

The present invention has been made by paying attention to this point. It is to be understood that the communication request signal from the slave station normally operates while maintaining the reliability of the serial communication between the master station and the slave station. A serial communication device capable of performing self-diagnosis,
It is an object to provide a serial communication method and a storage medium.

[0122]

In order to achieve the above object, a serial communication apparatus according to the present invention comprises a transmission line for connecting one master station and a plurality of slave stations in a loop, wherein the master station is connected to the master station. In a serial communication device that performs serial communication via the transmission path with the slave station in response to a communication request generated inside the station or a communication request signal generated by each slave station, each slave station should send to the master station. When the signal changes, the master station generates the communication request signal, and the master station stores, in response to the generated communication request signal, information content received from the slave station; When storing new information content in the storage means, the second storage means for saving the information content held immediately before the new information content, and the information content stored in the first and second storage means, respectively. By comparing Self-diagnosis means for performing self-diagnosis as to whether or not normal serial communication is performed, wherein the self-diagnosis means executes the self-diagnosis only when the serial communication device is in a predetermined operation state. It is characterized by.

Preferably, the self-diagnosis means compares the information contents stored in the first and second storage means with respect to all bits on a bit-by-bit basis, and determines whether both of the stored information contents are the same for all bits. When we are
Self-diagnosis that abnormal serial communication is being performed,
When both stored information contents do not match even by one bit, self-diagnosis is made that normal serial communication is performed.

Preferably, said self-diagnosis means comprises:
When a self-diagnosis is made that abnormal serial communication is being performed, the information content saved in the second storage means is returned to the first storage means.

Further, preferably, the master station transmits at least one bit or more of a signal to be sent to the master station by the slave station to at least one or more preset slave stations among the plurality of slave stations. At least one bit of a signal that the slave station should send to the master station when the self-diagnosis is performed by the remote operation means capable of remote operation and the self-diagnosis means that abnormal serial communication is being performed. By operating the above, there is provided control means for controlling the self-diagnosis means to repeat the self-diagnosis.

Further, more preferably, when the self-diagnosis that the abnormal serial communication has been performed continuously for a predetermined number of times or more by the repetition of the self-diagnosis is performed, it is determined that the serial communication device has a communication failure. It is characterized by having judgment means.

In order to achieve the above object, a serial communication method according to the present invention comprises a transmission line connecting one master station and a plurality of slave stations in a loop, wherein the master station communicates inside the master station. In the serial communication method of an electronic device that performs serial communication via the transmission path with the slave station in response to a request or a communication request signal generated by each slave station, in each slave station, a signal to be sent to the master station changes. When you do
The master station generates the communication request signal, and the master station stores information content received from the slave station in the first storage means in response to the generated communication request signal, and stores new information in the first storage means. When the content is held, the information content held immediately before is saved in the second storage means, and only when the serial communication device is in a predetermined operation state, the information is stored in the first and second storage means. It is characterized in that self-diagnosis is made as to whether or not normal serial communication is performed by comparing the stored information contents.

Preferably, in the self-diagnosis, the first
And the information contents respectively stored in the second storage means are compared for all bits for each bit. When the stored information contents match for all bits, it is determined that abnormal serial communication is being performed. Diagnosis is performed, and when both of the stored information contents do not match even by one bit, self-diagnosis is made that normal serial communication is performed.

Preferably, in the self-diagnosis, when the self-diagnosis indicates that abnormal serial communication is being performed, the information content saved in the second storage means is returned to the first storage means. It is characterized by.

More preferably, the master station transmits at least one bit or more of a signal to be sent to the master station by the slave station to at least one or more preset slave stations among the plurality of slave stations. When the self-diagnosis enables self-diagnosis that abnormal serial communication is being performed, the remote control operates at least one bit of a signal to be sent to the master station by the remote control. The self-diagnosis is repeatedly performed.

[0131] More preferably, when the self-diagnosis that the abnormal serial communication has been performed continuously for a predetermined number of times or more by the repetition of the self-diagnosis is performed, it is determined that the electronic device has a communication failure. It is characterized by.

In order to achieve the above object, the storage medium of the present invention comprises a transmission line connecting one master station and a plurality of slave stations in a loop, wherein the master station transmits a communication request generated inside the master station. Or a slave medium according to a communication request signal generated by each slave station, including a serial communication method of an electronic device performing serial communication via the transmission path, a storage medium storing a computer-implementable program, In the serial communication method, in each of the slave stations, when a signal to be sent to the master station changes, the communication request signal is generated, and in the master station, from the slave station in accordance with the generated communication request signal. The received information content is stored in the first storage means, and when the new information content is stored in the first storage means, the information content held immediately before the new information content is saved in the second storage means, The Only when the real communication device is in a predetermined operation state, by self-diagnosing whether or not normal serial communication is performed by comparing information contents respectively stored in the first and second storage means. It is characterized by.

Preferably, in the self-diagnosis, the first
And the information contents respectively stored in the second storage means are compared for all bits for each bit. When the stored information contents match for all bits, it is determined that abnormal serial communication is being performed. Diagnosis is performed, and when both of the stored information contents do not match even by one bit, self-diagnosis is made that normal serial communication is performed.

Preferably, in the self-diagnosis, when the self-diagnosis indicates that abnormal serial communication is being performed, the information content saved in the second storage means is returned to the first storage means. It is characterized by.

Further, preferably, the master station transmits at least one bit or more of a signal to be sent to the master station by the slave station to at least one or more preset slave stations among the plurality of slave stations. When the self-diagnosis enables self-diagnosis that abnormal serial communication is being performed, the remote control operates at least one bit of a signal to be sent to the master station by the remote control. The self-diagnosis is repeatedly performed.

More preferably, when the self-diagnosis is made that abnormal serial communication has been performed continuously for a predetermined number of times or more by repeating the self-diagnosis, it is determined that the electronic device has a communication failure. It is characterized by.

[0137]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 are flowcharts showing the procedure of the serial communication apparatus according to the first embodiment of the present invention, in particular, the serial communication processing which is a part of the control processing executed by the CPU of the master station m. And corresponds to FIG.

The serial communication apparatus of the present embodiment differs from the above-described conventional serial communication apparatus in a part of the serial communication processing (specifically, a communication request signal from a slave station normally operates normally). (A self-diagnosis process for self-diagnosis is added), and the same hardware as the above-described conventional serial communication device (FIGS. 7 to 9) is used. 1 and FIG.
Steps for performing the same processing as those described above are denoted by the same reference numerals, and description thereof will be omitted.

Before describing the normal communication processing, the configuration of a program executed by the CPU of the main station will be briefly described.

This program is configured by task type parallel processing. In other words, each independent control program configures a plurality of tasks, and executes initialization settings of memory and ports by resetting the CPU after turning on the power,
A program called a monitor program for controlling the start operation of each task is executed.

Each task is processed in parallel and executed in real time. The normal communication task (processing) in the serial communication task shown in FIG. 2 and FIG. 3 is also started by the monitor program, and returns to the monitor program once after executing a predetermined processing operation. Is made. Similarly, another task executes a predetermined processing operation and temporarily stops, but is started again to execute a subsequent control operation. As a result, the respective tasks perform parallel processing by sequentially executing predetermined processing operations, and the operation of the entire apparatus is controlled.

The cooperation between the tasks is performed by a memory accessed by each task.

Hereinafter, the present embodiment will be described.
The programs described below are tasks that are similarly processed in parallel, but are described as one connected program process for ease of description.

When the serial communication task (processing) described with reference to FIG. 12 is started by the monitor program, as described in the conventional example, in step S103, the serial communication task (processing) is connected to the current communication transmission line by the initialization communication processing. The memory reset of the slave station arrangement order is executed.

When the resetting of the memory is completed, the first normal communication after the initialization communication processing is performed in step S10.
6 or S107 is shifted to normal communication processing in step S108.

In the conventional example, a communication request generated inside the main station is determined in step S106, and the process proceeds to step S107.
Was used to determine the communication request signal from the slave station. However, in the present embodiment, the order is reversed, and step S1 is performed.
After determining the communication request signal from the slave station at 07, a communication request generated inside the master station is determined at step S106. This is because at the time of serial communication execution in the case where there is a communication request from the slave station, the information content before and after the execution of the serial communication is determined to be in a state of change, and the information content is not changed despite the slave station communication request. In order to determine whether there is any inconsistency in the communication execution result, as described in the conventional example, if there is a communication request from either the master station or the slave station, serial communication is executed and information exchange is terminated. Because it is different from what you do. That is, in the present embodiment, in order to determine inconsistency in the communication execution result, it is important whether serial communication is a communication request within the master station or a communication request signal from a slave station. This is because there is a ranking. Therefore, in this embodiment, when executing serial communication, it is necessary to confirm whether or not there is a communication request signal from a slave station anyway.

If it is determined in step S107 that the communication request signal from the slave station is off, the flow shifts to step S106 to check the communication request flag in the master station. Step S1
If it is determined that there is no communication request even at 06 (master station communication request flag = 0), the process proceeds to step S112 in FIG. 2, and the present serial communication process is ended once again until it is determined at steps S107 and S106 that there is a communication request. Loop through the program.

If only the communication request flag in the main station is set, the process proceeds from step S107 to step S106.
Proceeding to S108, serial communication by normal communication is executed. In this normal communication process, as described in the conventional example,
Upon completion, a communication error is checked in step S109.

If there is an abnormality in the normal communication processing, the process proceeds from step S110 to step S111 to operate in the same manner as in the conventional example. On the other hand, if there is no abnormality in the normal communication processing, in step S4 in FIG. It is checked in the state of the slave request flag whether or not to execute the slave communication request self-diagnosis processing. Here, since it is determined that only the communication request flag in the master station is set, the slave request flag is determined to be reset, the process proceeds to step S112, and the present serial communication process ends.

Next, the slave station communication request self-diagnosis processing which is a feature of the present invention will be described.

If it is determined that the communication request signal from the slave station is on regardless of the presence or absence of a communication request in the master station, the process moves from step S107 to step S1 and the serial communication device of the present embodiment is applied. Operating state of an electronic device (for example, an electrophotographic device). As described above, in the operation state detection of the device, the device control is performed in parallel with various tasks, and information exchange between the tasks is not particularly illustrated, but is assigned to the CPU in advance. The latest state is updated in the memory of each task as shown in FIG. Therefore, the contents of the relevant memory required by another task beyond the task can be checked by specifying the memory address from outside the task. As a result, the operation state of the device can be detected by designating the memory contents allocated in advance, and in step S1, it is checked whether the operation state of the entire apparatus is a standby state.

If printing is being performed, the slave station does not perform communication request self-diagnosis processing to prevent transmission delay of sensors and the like from the slave station.
Proceeding from step S1 to step S108 without performing anything, the normal communication processing is executed. On the other hand, if it is determined in step S1 that the apparatus is in the standby state, it is not necessary to prevent the transmission delay of the sensor and the like from the slave station. Proceeding to S2, an instruction is issued to execute a slave station communication request self-diagnosis process.

That is, in step S2, a slave request flag for instructing to check a change state of the content of the return information from the slave before and after the normal communication is set, and in step S3,
The content of the return information from the slave station stored and held by the previous serial communication is temporarily saved in another memory area. Specifically, in the present embodiment, the upper 4 bits (indicated by “Zn” in the figure) of the memory called the reset slave parallel input information shown in FIG. Is a memory area for temporarily saving the return information content. In other words, as described in the conventional example, the content of the return information received from the slave station through the serial communication is stored in the lower 4 bits of the memory called the slave parallel input information, and the slave communication request information of the present embodiment is stored. When executing the diagnostic process, the upper 4 bits of the unused parallel input information of the slave station that are not used are used as input information memory for temporary saving.

In step S3, the contents of the return information from the slave station before serial communication are saved in the upper 4 bits of the slave station parallel input information. In step S108, the normal communication processing is performed as in the conventional example. If there is no communication error in S109, the process proceeds to step S4. If it is determined in step S109 that there is a communication error, regardless of the validity or invalidity of the information exchange content referred to in the present embodiment, a slave station communication request self-diagnosis process is performed to execute retry communication in steps S110 and S111. Is suspended. On the other hand, if there is no communication error in step S109, the process proceeds to step S3, and the slave request flag is checked.

The slave station request flag is in the set state only when passing through the above-described steps S107 and S1, and in this case, the process proceeds to step S5 and thereafter.
That is, the slave station communication request self-diagnosis processing after step S5 is executed only when the operation of the entire apparatus is in the standby state. Therefore, even if the communication is performed by the communication request signal from the slave station, if the slave request flag is not set, one communication operation ends in the normal communication processing as described in the conventional example.

In step S4, if it is determined in step S2 that the slave request flag has been set, the flow advances to step S5 to reset the slave request flag. In step S6, the temporarily saved slave from the slave before the normal communication is reset. The contents of the upper 4 bits storing the return information and the contents of the lower 4 bits of the updated return information from the slave station after the normal communication are compared for each bit.

Then, in step S7, it is determined whether or not all the information contents match as a result of the comparison for every bit. As a result, if there is one or more bits that do not match,
It is determined that the information exchange by the executed normal communication process has been established, and the process proceeds to step S8, where the slave station request abnormality counter is cleared, and the process proceeds to step S112. In other words, when the information content from the slave station is updated, the content of the update information changes by one or more because the normal communication was performed by generating and executing a slave station communication request. Therefore, if it is determined that there is no match between the information contents from the slave station before and after the communication, it is updated to the latest information from the slave station, and one communication operation ends.

On the other hand, if it is determined in step S7 that all the information contents match as a result of the comparison for every bit, it is determined that the information content by the executed normal communication processing has not been established. That is, similarly, it is determined that there is no updated information content in spite of the normal communication executed by generating the slave station communication request, and the generation of the communication request signal from the slave station is inconsistent. It is thought that there is.

As described above, when it is determined that the comparison results of the information contents from the slave station before and after the communication match, noise or the like enters the communication request signal from the slave station or the shift transfer, and
This is because it can be inferred that the information exchange has been completed without any error being detected by the various error detection processes. In any case, the information exchange by the executed normal communication is determined to be unsuccessful and invalidated, so that the content of the slave station information set in the master station can be returned to the previous state, and the subsequent communication operation can be continued. To

In order to continue the communication operation, in step S9, the state is returned to the state before the execution of the normal communication executed this time. That is, the upper 4-bit portion of the slave parallel input information, which is the temporarily saved slave information content, is transferred to the lower 4-bit portion of the slave parallel input information.

Further, at step S10, the slave station request abnormality counter is incremented, and the routine goes to step S11.
Whether the contradiction in the slave station communication request has occurred continuously for a predetermined number of times or more is determined by the value of the slave station abnormality counter. As a result, if within the predetermined value, the operation proceeds to step S112 only by simply invalidating the result of the executed normal communication,
This normal communication ends. On the other hand, in step S11,
If the result is equal to or more than the predetermined value, the serial communication process is temporarily terminated after setting the retry counter value to a predetermined value or more at once in step S12.

Next, when the serial communication process is started, the process proceeds to the communication failure process from the judgment in step S101, and as described in the conventional example, the subsequent serial communication is stopped and the communication for the device failure is performed. The serviceman is called as a failure.

In this embodiment, if the information exchange is not established in the slave station communication request self-diagnosis processing, the slave station information content of the master station is returned to the original state. For example, the parallel output state of the slave station may be temporarily initialized by soft reset to continue normal communication, and the present invention is not particularly limited.

As described above, in the present embodiment, when the operation of the electronic device to which the serial communication device is applied is, for example, during printing, that is, during the operation in which normal communication is frequently performed, the slave station communication request self-diagnosis is performed. On the other hand, when the operation of the electronic device is, for example, in a standby state, that is, during an operation in which the frequency of the normal communication is considered to be low (only at this time), the slave communication request self-diagnosis processing is performed. The time required for communication is kept to a minimum and the delay of information from the slave is prevented, while the self-request of the slave communication request signal, which is an important signal source for maintaining bidirectional serial communication, is performed. By performing the diagnosis, the reliability of serial communication can be further improved. Further, in the present embodiment, the slave station communication request self-diagnosis processing
Since this is realized by using an unused area in the memory and adding a small amount of processing to the conventional serial communication processing, self-diagnosis can be performed while suppressing an increase in manufacturing cost.

Next, a serial communication device according to a second embodiment of the present invention will be described.

The serial communication device according to the present embodiment, like the serial communication device according to the first embodiment, performs normal communication based on the presence or absence of a communication request signal from a slave station received by a device during standby. The serial communication device according to the present embodiment is configured so as to determine the change state of the slave station information contents before and after and determine whether information exchange is unsuccessful based on whether or not an inconsistency has occurred. The processing after determining that the information exchange has failed is different from the serial communication device according to the first embodiment.

Specifically, it is determined that the information exchange by the normal communication is not established, and the information content from the slave station is returned to the information content by the previous communication. By controlling at least one of the parallel input terminals of the slave stations to generate a communication request signal for the slave station, the slave communication request described in the first embodiment can be controlled. The difference is that the same slave station communication request self-diagnosis processing is repeatedly executed immediately after the self-diagnosis processing ends.

Accordingly, in the present embodiment, the hardware of FIG. 4 which is an improvement of the hardware of FIG. 9 used in the conventional example is used as the hardware, and the serial communication processing in the first embodiment is used as the serial communication processing. Figures 1 and 2 used
The serial communication processing of FIGS. 5 and 6 which is an improvement of the serial communication processing of FIG.

FIG. 4 is different from the conventional example (FIG. 9) in that an output signal called request operation is supplied from master station m to (one bit of) the parallel input terminal of slave station s12. It is. The slave having the parallel input terminal to which the request operation signal is supplied need not be particularly limited to the slave s12, and is connected to one or more terminals of one or more slaves among the slaves existing in the transmission path. It should just be.

The communication request signal from the slave station is transmitted to the phase control counter circuit 11 by the bit-by-bit comparison circuit constantly monitored by the EXOR circuit A3 shown in FIG. And a communication request signal to be returned to the master station at a phase timing generated by the circuit composed of the decoding circuit B12 and the decoding circuit B12.

As described above, with the extremely simple configuration of connecting the parallel input terminal of the slave station which can be directly operated by the master station to any slave station existing on the transmission line, the master station can control the master station under its own control. The communication request signal from the slave station can be operated. Hereinafter, the operation of the communication request signal for the slave station performed by the master station is referred to as “slave station communication request remote operation”. Therefore, by performing the slave station communication request remote operation, the slave station communication request self-diagnosis can be easily executed again.

Hereinafter, the serial communication processing which is a part of the control processing executed by the CPU of the master station m will be described with reference to FIG. 5 and FIG.
Note that the flowchart of FIG. 5 is the same as the flowchart of FIG. 1, and a description thereof will be omitted.

In FIG. 6, when the information stored in the memory is returned in step S9, the slave station request abnormality counter is incremented in step S10, and the routine goes to step S11.

Then, in step S11, as described in the first embodiment, it is determined whether or not inconsistency in the slave station communication request has occurred continuously for a predetermined number of times or more, based on the value of the slave station abnormality counter. If the result is equal to or greater than a predetermined value,
In step S12, the retry counter value is set to a predetermined value or more at once, and after the present serial communication process is once completed, the next serial communication process is started. According to the determination in step S101 in FIG. Then, as described in the conventional example, the subsequent serial communication is stopped and a serviceman call is made as a communication failure due to a failure of the device.

On the other hand, if it is determined in step S11 that the value is within the predetermined value, the flow shifts to step S21 to change the state of the requested operation output signal (that is, the slave station communication request remote operation is performed). Then, the serial communication process is temporarily ended.

The slave station communication request remote operation processing in step S21 basically only needs to change the state of the request operation output signal, and when the next serial communication processing is executed by that processing, the operation returns to the state shown in FIG. In step S107, a communication request signal from the slave station is received. In step S1, it is determined that the apparatus is on standby, and the slave station communication request self-diagnosis processing is repeatedly executed again. As a result, the slave station communication request self-diagnosis processing is repeatedly executed until the information exchange execution is established or the communication failure is determined.

Note that the slave station communication request remote operation process in step S21 does not merely change the state of the request operation output signal, but also uses the timer of the CPU itself to output the request operation output signal at a predetermined time period. By changing the state of the signal, the slave station communication request self-diagnosis processing may be periodically and repeatedly executed until the information exchange execution is established or until it is determined that a communication failure has occurred.

In communication modes other than serial communication,
Basically, if the communication mode is in accordance with the communication request from each slave station, it is possible to determine the change state of the return information content from the slave station before and after the communication before and after each communication, depending on the presence or absence of the communication request. It is possible to determine whether or not a contradiction has occurred, and to easily execute the self-diagnosis of the communication request while communicating.

As described above, in the present embodiment, when it is determined by the slave communication request self-diagnosis processing that the information exchange by the normal communication is not established, the slave communication request remote operation is performed and the information exchange by the normal communication is performed. The self-diagnosis process of the slave station communication request is repeated until the communication is established or until the communication failure is determined. Or accidentally,
Self-diagnosis can be performed intensively in a short time.

A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium in the storage medium. It goes without saying that the object of the present invention is also achieved by reading and executing the stored program code.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
CD-R, magnetic tape, nonvolatile memory card, RO
M6 or the like can be used. Further, the program code may be supplied from a server computer via a communication network.

When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS or the like running on the computer based on the instructions of the program code. Does a part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

[0186]

As described above, according to the first, sixth, or eleventh aspect of the present invention, normal serial communication is performed when the apparatus is in an operating state in which the communication frequency is high, for example. Without self-diagnosis of whether
By concentrating only on the original serial communication, the time spent for communication is kept to a minimum and the information transmission delay from the slave station is prevented. In a specific operating state, self-diagnosis is performed to determine whether or not normal serial communication is being performed. In addition to the original serial communication, slave communication is an important signal source for maintaining bidirectional serial communication. By performing the self-diagnosis of the request signal, the reliability of the serial communication can be further improved while suppressing the information delay from the slave station. Further, if the second storage means is set in an area where the first storage means is not used, it is possible to suppress an increase in manufacturing cost due to the self-diagnosis.

According to the present invention, when a self-diagnosis is made that abnormal serial communication is being performed, a signal transmitted from the slave station to the master station by remote operation is determined by remote control. By operating at least one bit or more, the self-diagnosis is repeatedly performed.
Even when a self-diagnosis is made that abnormal serial communication is being performed, it is possible to perform a self-diagnosis intensively in a short time whether the self-diagnosis is caused by a device failure or an accidental occurrence.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a procedure of a serial communication process executed by a serial communication device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a continuation of the serial communication process of FIG. 1;

FIG. 3 is a diagram showing a memory map after the memory map of FIG. 10 is used in a slave station communication request self-diagnosis process.

FIG. 4 is a block diagram illustrating a schematic configuration of an electronic apparatus to which a serial communication device according to a second embodiment of the present invention is applied.

FIG. 5 is a flowchart illustrating a procedure of a serial communication process executed by the serial communication device of FIG. 4;

FIG. 6 is a flowchart showing a continuation of the serial communication process of FIG. 5;

FIG. 7 is a block diagram illustrating a schematic configuration of an electronic apparatus to which a conventional serial communication device is applied.

FIG. 8 is a block diagram showing a detailed configuration of one of the slave stations in FIG. 7;

FIG. 9 is a block diagram illustrating an example of an electronic device configured by omitting some slave stations installed as options from the electronic device of FIG. 7;

FIG. 10 is a diagram showing an example of a memory map used when the serial communication device in FIG. 7 performs information exchange.

FIG. 11 is a diagram showing a memory map after the memory map of FIG. 10 is reset by initialization communication.

FIG. 12 is a flowchart illustrating a procedure of a serial communication process executed by the serial communication device of FIG. 7;

13 is a flowchart showing a detailed procedure of an initialization communication process in FIG.

14 is a flowchart showing a detailed procedure of a normal communication process in FIG.

FIG. 15 is a flowchart showing a continuation of the normal communication process of FIG. 14;

[Explanation of symbols]

 Reference Signs List 1 input selector circuit 2 input latch circuit 3 EXOR circuit A 4 shift register circuit 5 double read latch circuit 6 EXOR circuit B 7 output latch circuit 8 gate circuit 9 decode circuit A 10 clock number counter circuit 11 phase control counter circuit 12 decode circuit B m master station s1 to s12 slave station

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (15)

[Claims] 1. A transmission line for connecting one master station and a plurality of slave stations in a loop, wherein the master station responds to a communication request generated inside the master station or a communication request signal generated by each of the slave stations. The slave station and the serial communication device that performs serial communication via the transmission path, wherein each of the slave stations generates the communication request signal when a signal to be sent to the master station changes, and the master station A first storage unit for storing information content received from the slave station in response to the generated communication request signal; and a first information storage unit for storing new information content in the first storage unit.
By comparing the information contents stored in the first and second storage means with the second storage means for evacuating the information content held immediately before, whether or not normal serial communication is performed A self-diagnosis unit for performing self-diagnosis of the serial communication device, wherein the self-diagnosis unit executes the self-diagnosis only when the serial communication device is in a predetermined operation state. 2. The self-diagnosis means compares the information contents stored in the first and second storage means with respect to all bits on a bit-by-bit basis. Self-diagnosis that abnormal serial communication has been performed, and when the stored information contents do not match even one bit,
2. The serial communication device according to claim 1, wherein self-diagnosis is performed that normal serial communication is performed. 3. The self-diagnosis means returns the information saved in the second storage means to the first storage means when the self-diagnosis means makes a self-diagnosis that abnormal serial communication is being performed. The serial communication device according to claim 1. 4. The master station can remotely control at least one bit or more of a signal to be sent to the master station by at least one or more preset slave stations among the plurality of slave stations. When the self-diagnosis unit performs a self-diagnosis that abnormal serial communication has been performed, the remote operation unit operates at least one bit of a signal to be sent from the slave station to the master station. 4. The serial communication device according to claim 2, further comprising control means for controlling the self-diagnosis means to perform self-diagnosis repeatedly. 5. When the self-diagnosis is performed by performing the self-diagnosis repeatedly and abnormal serial communication is performed continuously for a predetermined number of times or more, the serial communication device includes a determination unit that determines that a communication failure has occurred. The serial communication device according to claim 4, wherein: 6. A transmission line for connecting one master station and a plurality of slave stations in a loop, wherein the master station responds to a communication request generated inside the master station or a communication request signal generated by each of the slave stations. The slave station and the serial communication method for an electronic device that performs serial communication via the transmission path, wherein each slave station generates the communication request signal when a signal to be sent to the master station changes. In the master station, the information content received from the slave station in response to the generated communication request signal is stored in the first storage means, and when the new information content is stored in the first storage means,
The information content held immediately before is saved in the second storage means, and only when the serial communication device is in a predetermined operation state,
A serial communication method, wherein self-diagnosis is performed as to whether or not normal serial communication is performed by comparing information contents stored in the first and second storage units. 7. In the self-diagnosis, the first and second
The information contents respectively stored in the storage means are compared for all bits for each bit, and when the stored both information contents match for all bits, a self-diagnosis is made that abnormal serial communication is being performed, 7. The serial communication method according to claim 6, wherein when both of the stored information contents do not match even by one bit, a self-diagnosis is made that normal serial communication is performed. 8. In the self-diagnosis, when a self-diagnosis that abnormal serial communication is being performed is made, the second self-diagnosis is performed.
8. The serial communication method according to claim 6, wherein the information content saved in said storage means is returned to said first storage means. 9. The master station can remotely control at least one bit or more of a signal to be sent to the master station from at least one or more preset slave stations among the plurality of slave stations. When the self-diagnosis determines that abnormal serial communication is being performed, at least one of the signals to be sent from the slave station to the master station by the remote operation is performed.
9. The serial communication method according to claim 7, wherein the self-diagnosis is repeatedly performed by operating more than one bit. 10. The repetitive execution of the self-diagnosis,
10. The serial communication device according to claim 9, wherein when a self-diagnosis is made that abnormal serial communication has been performed continuously for a predetermined number of times or more, the electronic device is determined to have a communication failure. 11. A transmission line for connecting one master station and a plurality of slave stations in a loop, wherein the master station responds to a communication request generated inside the master station or a communication request signal generated by each of the slave stations. And a slave medium, including a serial communication method of an electronic device that performs serial communication via the transmission path, a storage medium storing a computer-implementable program, wherein the serial communication method includes: The communication request signal is generated when the signal to be sent to the master station changes, and the master station stores the information content received from the slave station in the first storage means in response to the generated communication request signal. When storing new information content in the first storage means,
The information content held immediately before is saved in the second storage means, and only when the serial communication device is in a predetermined operation state,
A storage medium for performing self-diagnosis as to whether or not normal serial communication is performed by comparing information contents stored in the first and second storage means. 12. In the self-diagnosis, information contents respectively stored in the first and second storage means are compared for all bits for each bit, and both stored information contents are matched for all bits. Self-diagnosis that abnormal serial communication has been performed, and when the stored information contents do not match even one bit,
12. The storage medium according to claim 11, wherein self-diagnosis is performed that normal serial communication is performed. 13. In the self-diagnosis, when the self-diagnosis that an abnormal serial communication is performed is performed, information stored in the second storage unit is returned to the first storage unit. The storage medium according to claim 11, wherein 14. The master station can remotely control at least one bit or more of a signal to be sent to the master station from at least one or more preset slave stations among the plurality of slave stations. When the self-diagnosis determines that abnormal serial communication is being performed, at least one of the signals to be sent from the slave station to the master station by the remote operation is performed.
14. The storage medium according to claim 12, wherein the self-diagnosis is repeatedly performed by operating more than one bit. 15. By repeatedly executing the self-diagnosis,
15. The storage medium according to claim 14, wherein when the self-diagnosis is performed that serial communication that is not normal has been performed continuously for a predetermined number of times or more, the electronic device is determined to have a communication failure.