JPH11163885A - Serial load controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an equipment from being damaged by communication failure by providing slave controllers with communication error detecting means which detect communication error with a master controller and stopping a load if the communication error is detected. SOLUTION: Slave controlling parts 4002 to 4004 which receive a load control request from a master controlling part 4001 by serial communication control corresponding load. Each slave controlling part 4002 to 4004 outputs data that is received at the time of WRITE to a corresponding circuit and sends signal that senses a corresponding state at the time of READ. When received data includes abnormal data and addresses, it is decided that a communication failure takes place and when normal data is not sent for more than a fixed time, a prescribed safe state is made such as making a control output to a load high impedance, the control of the load is stopped and damage of the entire device is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial load control device for controlling a corresponding load by a slave controller which receives a load control request by serial communication from a master controller.

[0002]

2. Description of the Related Art A plurality of loads of an apparatus such as an image forming apparatus are reduced by one.
The drive control method using one controller increases the size of the device and increases the load, so the space cost for wiring between the controller and each load also increases. For example, as shown in FIG. 6, there is known a method in which a slave controller for driving and controlling the load is arranged near the load, and the slave controller and the master controller communicate with each other by serial communication.

[0003]

When such a method is adopted, the wiring for load control requires only a short wiring between the slave controller located near the load and the wiring between the master controller and the slave controller. Since serial communication is also performed, only a small number of wires are required, and wiring costs can be reduced. Further, such a method is very effective when the number of loads to be controlled is large and the loads are far from the controller.

However, in such a method, the load is not directly driven by the master controller, but is driven and controlled by the slave controller according to a command received from the master controller via the serial communication line by the slave controller. In such a case, the drive control of the load by the slave controller may be erroneously performed.

[0005] It is an object of the present invention to provide a serial load control device which can solve the above-mentioned problems and can prevent damage to the device due to a communication failure.

[0006]

According to a first aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller which receives a load control request through serial communication from a master controller, wherein the slave controller comprises: A communication error detecting means for detecting a communication error with the controller is provided, and when a communication error is detected by the communication error detecting means, control is performed to stop the load.

According to a second aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. Communication error detecting means for detecting an error, and counting means for counting the number of communication errors detected by the communication error detecting means, wherein the number of communication errors counted by the counting means exceeds a predetermined number. In this case, the load is controlled to be stopped.

According to a third aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. Communication error detecting means for detecting an error, counting means for counting the number of communication errors detected by the communication error detecting means,
A storing unit that stores the number of communication errors counted by the counting unit in accordance with the priority in the descending order; and an extracting unit that extracts a priority corresponding to the number of communication errors from the storing unit, wherein the priority is extracted by the extracting unit. In this case, the load having the extracted priority is controlled to be stopped when the load is detected.

According to a fourth aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. Communication error detecting means for detecting an error, counting means for counting the number of communication errors detected by the communication error detecting means,
Storing means for storing the reference priority corresponding to the number of communication errors counted by the counting means in ascending order of reference priority, and extracting means for extracting the reference priority corresponding to the number of communication errors from the storing means; When the priority is taken out, control is performed so as to stop loads having a priority equal to or higher than the taken out reference priority.

According to a fifth aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. A communication error detecting means for detecting an error, wherein the master controller is reset when a communication error is detected by the communication error detecting means.

[0011] In any one of the first to fifth aspects, the communication error detecting means may detect the communication error as a communication error if the communication error does not recover after a predetermined time has elapsed since the occurrence of the communication error. it can.

According to a seventh aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. A communication error detecting means for detecting an error is provided, and when a communication error is detected by the communication error detecting means, a control output to a load is set to a high impedance state.

According to an eighth aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. Communication error detecting means for detecting an error, and counting means for counting the number of communication errors detected by the communication error detecting means, wherein the number of communication errors counted by the counting means exceeds a predetermined number. In this case, the control output to the load is set to a high impedance state.

According to a ninth aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller which receives a load control request by serial communication from a master controller, wherein the slave controller communicates with the master controller. Communication error detecting means for detecting an error, counting means for counting the number of communication errors detected by the communication error detecting means,
A storing unit that stores the number of communication errors counted by the counting unit in accordance with the priority in the descending order; and an extracting unit that extracts a priority corresponding to the number of communication errors from the storing unit, wherein the priority is extracted by the extracting unit. In this case, the control output to the load having the extracted priority is set to a high impedance state.

According to a tenth aspect of the present invention, there is provided a serial load control device for controlling a corresponding load by a slave controller which receives a load control request by serial communication from a master controller, wherein the slave controller comprises:
Communication error detection means for detecting a communication error with the master controller; counting means for counting the number of communication errors detected by the communication error detection means; Storing means for storing the priorities corresponding to the highest priority, and extracting means for extracting a reference priority corresponding to the number of communication errors from the storing means, and when the reference priority is extracted by the extracting means, the extracted reference. A control output to a load having a priority higher than the priority is set to a high impedance state.

[0016] In any one of claims 7 to 10,
The communication error detecting means can detect the communication error as a communication error when the communication failure does not recover even after a predetermined time has elapsed since the occurrence of the communication failure.

[0017]

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

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
An embodiment will be described. This is an example of a color image forming apparatus, and the structure of this apparatus is shown in FIG. The color image forming apparatus shown in FIG. 2 includes a reader unit and a printer unit.

The reader section of FIG. 2 will be described. In FIG. 2, reference numeral 302 denotes a document feeder (DF) for feeding a document to a platen glass (platen) 301. There is also a configuration in which a mirror pressure plate (not shown) is mounted instead of the document feeder 302. Reference numerals 303 and 304 denote light sources, which illuminate a document on the platen glass 301. The light sources 303 and 304 include a halogen lamp or a fluorescent lamp. 305 and 306 are reflecting umbrellas for condensing the light from the light sources 303 and 304 onto the original. Reference numerals 307 to 309 denote mirrors for guiding reflected light or transmitted light from the document to the condenser lens 310. Reference numeral 314 denotes a carriage, and the halogen lamp 30
3, 304, reflecting umbrellas 305, 306, and mirror 307
Is housed. Reference numeral 315 denotes a carriage in which mirrors 308 and 309 are accommodated. 101 is a CCD (ch
arge coupled device), which is mounted on the substrate 311 and converts an optical signal passing through the condenser lens 310 into an electric signal. In the case of a color sensor, the CCD 101 may be a three-line CCD even if RGB color filters are inlined on a one-line CCD in RGB order.
In D, an R filter, a G filter, and a B filter may be arranged for each CCD, or the filter may be on-chip, or the filter may be configured differently from the CCD.

Reference numeral 312 denotes an image processing unit.
To process the image signal from. 313 is an interface (I / F) unit with a computer or the like.

The carriage 314 is moved at a speed V and the carriage 315 is moved at a speed V / 2 mechanically in a direction perpendicular to the electrical scanning (main scanning) direction of the CCD 101, so that the entire surface of the document is scanned (sub scanning). Scan).

The printer section shown in FIG. 2 will be described. In FIG. 2, reference numerals 340 and 341 denote cassettes for storing recording paper and the like. Reference numerals 338 and 339 denote pickup rollers for separating recording paper and the like from the cassettes 340 and 341 one by one. Reference numerals 336 and 337 denote paper feed rollers for supplying recording paper and the like separated by the pickup rollers 338 and 339 onto the transfer belt 333. Reference numeral 346 denotes an adsorption charger, and the transfer belt 33
The recording paper and the like are charged in cooperation with the transfer belt roller 348 for driving the recording paper 3, and the recording paper and the like are attracted to the transfer belt 333. A paper edge sensor 347 detects the edge of a recording sheet or the like on the transfer belt 333. The detection signal of the paper leading edge sensor 347 is sent from the printer unit to the reader unit, and is used as a sub-scanning synchronization signal when a video signal is sent from the reader unit to the printer unit.

Reference numeral 317 denotes a Y image forming unit, 318 denotes an M image forming unit, 319 denotes a C image forming unit, and 320 denotes a K image forming unit.

The Y image forming section 317 includes the LED array 21
0, a photosensitive drum 342, a developing device 322, and a primary charging device 321. The LED array 210 forms a latent image on the surface of the photosensitive drum 342 by light from the LED array 210. The primary charger 321 charges the surface of the photosensitive drum 342 to a predetermined potential to prepare for forming a latent image. The developing device 322 includes the photosensitive drum 342
The toner image is formed by developing the upper latent image.
The developing device 322 includes a sleeve 345 for applying a developing bias to develop.

The M image forming unit 318 includes the LED array 21
1, a photosensitive drum 353, a developing device 325, and a primary charging device 324. The LED array 211 forms a latent image on the surface of the photosensitive drum 353 by light from the LED array 211. The primary charger 324 charges the surface of the photosensitive drum 353 to a predetermined potential to prepare for forming a latent image. The developing device 325 includes the photosensitive drum 353
The toner image is formed by developing the upper latent image.
The developing device 325 includes a sleeve 356 for applying a developing bias to develop.

The C image forming unit 319 includes the LED array 21
2, a photosensitive drum 354, a developing device 328, and a primary charger 327. The LED array 212 forms a latent image on the surface of the photosensitive drum 354 by light from the LED array 212. The primary charger 327 charges the surface of the photosensitive drum 354 to a predetermined potential to prepare for forming a latent image. The developing device 328 includes the photosensitive drum 354
The toner image is formed by developing the upper latent image.
The developing device 328 includes a sleeve 357 for applying a developing bias to develop.

The K image forming section 320 includes the LED array 21
3, a photosensitive drum 355, a developing device 331, and a primary charging device 330. The LED array 213 forms a latent image on the surface of the photosensitive drum 355 by light from the LED array 213. The primary charger 330 charges the surface of the photosensitive drum 355 to a predetermined potential to prepare for forming a latent image. The developing device 331 includes a photosensitive drum 355
The toner image is formed by developing the upper latent image.
The developing device 331 includes a sleeve 358 for applying a developing bias to perform development.

Reference numeral 323 denotes a transfer charger, which is a transfer belt 3
The discharge is performed from the back surface of the transfer belt 33 to transfer the toner image on the photosensitive drum 342 to a recording paper or the like on the transfer belt 333. 326, a transfer charger;
The discharge is performed from the back surface of the transfer belt 3, and the toner image on the photosensitive drum 353 is transferred to a recording paper or the like on the transfer belt 333. Reference numeral 329 denotes a transfer charger, which is a transfer belt 333.
Is performed from the back surface of the transfer belt 333 to transfer the toner image on the photosensitive drum 354 to recording paper or the like on the transfer belt 333. Reference numeral 332 denotes a transfer charger which discharges from the back surface of the transfer belt 333 to transfer the toner image on the photosensitive drum 355 to recording paper on the transfer belt 333 or the like.

In this embodiment, since the transfer efficiency is good,
The cleaner is not located. It goes without saying that there is no problem even if the cleaner is mounted.

Reference numeral 349 denotes a static eliminator, and the transfer belt 3
This is for discharging the recording paper and the like on 33. Reference numeral 350 denotes a peeling charger, which prevents image disturbance due to peeling discharge when the recording paper or the like is separated from the transfer belt 333. Reference numerals 351 and 352 denote chargers before fixing, which charge the recording paper and the like separated from the transfer belt 333, and supplement the toner attraction force to prevent image disturbance. A fixing device 334 heat-fixes the toner image.
Reference numeral 335 denotes a paper discharge tray for storing discharged recording paper and the like.

Next, an image forming procedure by the printer unit will be described. When one sheet of recording paper stored in the cassette 340 is separated by the pickup roller 338, the recording paper is supplied onto the transfer belt 333 by the paper feeding rollers 336 and 337. The recording paper supplied to the transfer belt 333 is charged by the cooperation of the attraction charger 346 and the transfer belt roller 348, and is attracted to the transfer belt 333. afterwards,
The recording paper is conveyed by the transfer belt 333, and the Y and Y formed by the image forming units 317 to 320 on the recording paper
M, C, K toner images are transferred to transfer chargers 323, 326,
329 and 332, respectively. The recording paper that has passed through the K image forming section 320 is separated from the transfer belt 333 after being discharged by a discharging charger 349 in order to facilitate separation from the transfer belt 333. The separated recording paper is charged by pre-fixing chargers 351 and 352 in order to supplement the toner attraction force and prevent image disturbance, and thereafter,
The toner image is heat-fixed by the fixing device 334, and
35 is discharged.

Next, the digital image processing unit 31 shown in FIG.
2 will be described with reference to FIG. 3 showing the configuration of the digital image processing unit 312. The analog image signal from the CCD 101 is clamped / amplified / S / H (sample a
nd hold) · A / D (analog-to-digital) unit 102 performs sample-and-hold, clamps the dark level of the analog image signal to a reference potential, and amplifies it to a predetermined amount. Is not limited), A /
It is D-converted and converted into, for example, a digital signal of 8 bits for each of RGB. Then, these RGB signals are subjected to shading correction and black correction by the shading unit 103, and thereafter, the connection / MTF correction / document detection unit 10
According to 4, when the CCD 101 is a three-line CCD, the splicing process differs in the reading position between the lines, so the delay amount for each line is adjusted according to the reading speed, and a signal is output so that the reading positions of the three lines become the same. The timing is corrected, and the MTF correction changes the reading MTF depending on the reading speed and the magnification, so that the change is corrected, and the document detection recognizes the document size by scanning the document on the platen glass.

The digital signal whose read position timing has been corrected is input to the CCD 10 by the input masking unit 105.
1 and the light sources 303 and 304 and the reflector 30
The spectral characteristics of 5 and 306 are corrected and input to the selector 106 which can be switched to an external I / F signal. The output signal from the selector 106 is color space compression / background removal / LO
It is input to the G conversion unit 107 and the background removal unit 115.

The background removal unit 115 removes the background from the input signal, and then generates a black character signal from the document by the black character determination unit 116 that determines whether or not the document is a black character.

On the other hand, the color space compression / background removal / LOG conversion section 107 performs color space compression, that is, determines whether or not the read image signal is within the range that can be reproduced by the printer. As is, if it is not included, the image signal is corrected so that it is within the range that can be reproduced by the printer, then the background removal processing is performed,
After that, the RGB signals are converted into CMY signals by LOG conversion, and the obtained CMY signals are converted to the black character determination unit 11.
In order to correct the decision signal and the timing generated in step 6,
The timing is adjusted by the delay unit 108.

The CMY signal from the delay unit 108 and the determination signal generated by the black character determination unit 116 are
Moiré is removed by the moiré removing unit 109, and then
The scaling processing section 110 performs scaling processing in the main scanning direction.
A signal obtained by processing in the scaling unit is converted into a CMYK signal by a UCR process from a CMY signal in a UCR / masking / black character reflecting unit 111, and is corrected to a signal present at the output of the printer by a masking process. On the other hand, the determination signal is fed back to the CMYK signal. Then
The signal from the UCR / masking / black character reflection unit 111 is subjected to density adjustment by the γ correction unit 112, and then smoothing or edge processing is performed by the filter unit 113.

Next, the printer processing section will be described with reference to FIG. The signal from the image processing unit 312 is converted from an 8-bit CMYK multi-level signal into a binary signal by the binary conversion unit 201 in synchronization with the paper edge signal from the paper edge sensor 347 (FIG. 2). This conversion method may be any of a dither method, an error diffusion method, and an improved error diffusion method. Then, based on the signal generated by the binary conversion unit 201, the LEDs 210 to 213 are driven by the LED driving units 206 to 209. As described above, the paper leading edge sensor 347 and the image forming units 322, 325, 32
Since the difference between the distances 8 and 331 is adjusted by the delay units 202 to 205, it is possible to print four colors at predetermined positions.

Next, FIG. 1 will be described. In FIG. 1, 4
Reference numeral 001 denotes a master control unit, which is arranged at the center of the rear surface of the image forming apparatus. Reference numeral 4002 denotes a slave control unit for controlling the paper feed unit load, which is arranged near the paper feed unit. Reference numeral 4003 denotes a slave control unit for controlling the discharge load, which is arranged near the discharge unit. 4004
Is a slave control unit for reader load control,
It is located near the leader.

Serial communication (clock, data) between the master control unit 4001 and each of the slave control units 4002 to 4004 via a serial communication line.
Has been done. The paper feeding unit includes loads such as a motor for driving the pickup rollers 338 and 339, the paper feeding rollers 336 and 337, and a clutch, for example. The ON / OFF control of these loads is performed by a command from the master control unit 4001 via a serial communication line.
When the slave control unit 4002 is issued to the slave control unit 4002 for controlling the sheet feeding load, the slave control unit 4002 interprets this and controls ON / OFF of the load of the sheet feeding unit.

Next, the serial communication procedure will be described with reference to FIG. The serial communication line is composed of a clock line in the direction from a master control unit (hereinafter also referred to as a master) to a slave control unit (hereinafter also referred to as a slave) and a bidirectional data line. Done.

The data is START (2 bits “1”
1 ", master-> slave) and COMMAND (3
Bit “00 *”; * -0: READ, 1: WRIT
E, master-> slave), ADDRESS (4 bits, master-> slave), DATA (8 bits, master <-> slave), and END (2 bits "00"master-> slave) And ACK (1 bit; 0: OK, 1: NG, master <-slave)
And PARITY (1 bit, master, <-slave).

Slave control units 4002, 400
3,4004 latches data from START and
At the time of RITE, the received data is output to an appropriate load control output, and at the time of READ, an appropriate load state is output to a data line. When the received data is abnormal, for example, when an unknown COMMAND is sent, when an address outside the area is specified, when an END is not received, etc. Output a load control output that turns off. The output value (1 or 0) that is turned off for each load is preset in the slave control unit.

When such a communication failure is detected by, for example, the slave control units 4002, 4003, and 4004, the slave control units 4002 and 404
Since the control of the load is stopped by 03,4004, it is possible to prevent damage to the present color image forming apparatus due to a communication failure. When a communication failure is detected, the slave control units 4002 and 400
Even if the control output to the load is set to high impedance according to 3,4004, damage to the present color image forming apparatus due to communication failure can be prevented. In this case, a pull-up / pull-down resistor can be provided in a direction in which the load is turned off outside the control output to each load to cope with the situation.

To detect a communication failure, the slave control units 4002, 4003, and 4004 have a watchdog timer, and this timer is cleared each time normal data is received from the master controller. This may be performed when normal data is not sent from the master controller 4001.

<Second Embodiment> This embodiment is a first embodiment.
In comparison with the embodiment, the load control method is different. In the first embodiment, when a communication failure is detected, the load control is immediately stopped. On the other hand, in the present embodiment, the slave control unit 4
002, 4003, and 4004 count the number of communication errors each time a communication error with the master control unit 4001 is detected. If the counted number of communication errors exceeds a predetermined number, the load Control stopped. Further, even when a communication failure is detected, the control output to the load is set to high impedance by the slave control units 4002, 4003, and 4004 to prevent damage to the color image forming apparatus due to the communication failure. Can be.

<Third Embodiment> This embodiment is a first embodiment.
In comparison with the embodiment, the load control method is different. In the first embodiment, when a communication failure is detected, the load control is immediately stopped. On the other hand, in the present embodiment, several levels of priorities are set according to the type of load, and the slave control unit 4002 is set from the load whose priority is set higher according to the number of detected communication failures. 400
The control of the load is stopped by 3,4004.
Further, even if the control output to the load is set to high impedance by the slave control units 4002, 4003, and 4004 instead of stopping the load control, it is possible to prevent damage to the color image forming apparatus due to a communication failure. Can be.

<Fourth Embodiment> This embodiment is a first embodiment.
In comparison with the embodiment, the load control method is different. In the first embodiment, when a communication failure is detected, the load control is immediately stopped. On the other hand, in the present embodiment, several stages of reference priorities are made to correspond to the counted number of communication errors in descending order, and according to the number of detected communication failures, a load having a priority equal to or higher than the reference priority is determined. Control stopped. Even if the control output to the load is set to high impedance by the slave control units 4002, 4003, and 4004 instead of stopping the load control, damage to the color image forming apparatus due to a communication failure can be prevented. .

<Fifth Embodiment> This embodiment is a first embodiment.
In comparison with the fourth embodiment, the control method when a communication failure is detected is different. That is, the first
In the fourth embodiment, the control of the load by the slave control units 4002, 4003, and 4004 is stopped, or the control output to the load is set to high impedance. On the other hand, in the present embodiment, the slave control units 4002, 4003, 40
A reset line for transmitting a reset signal is provided between the master control unit 4001 and the master control unit 4001. When the slave control units 4002, 4003, and 4004 continue to receive abnormal data, the master control unit 4001
Since there is a high possibility that some trouble has occurred on the side, the master controller 4001 is reset from the slave control units 4002, 4003, and 4004 via the reset line. Even in this case, it is possible to prevent damage to the present color image forming apparatus due to a communication failure.

As described above, in the first to fifth embodiments,
Although an example of a color image forming apparatus has been described, it goes without saying that the present invention can be applied to all apparatuses that control loads by serial communication.

[0050]

As described above, according to the present invention,
With the above configuration, there is an effect that the reliability of the device having the serial load control system can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of the color image forming apparatus shown in FIG.

FIG. 3 is a block diagram showing a configuration of a digital image processing unit 312 shown in FIG.

FIG. 4 is a block diagram illustrating a configuration of a printer processing unit.

FIG. 5 is an explanatory diagram for explaining a serial communication procedure.

FIG. 6 is an explanatory diagram for explaining serial load control.

[Explanation of symbols]

4001 master control unit 4002, 4003, 40004 slave control unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Yamaguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tetsuro Fukusaka 3-30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor Michio Kawase 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. A serial load control device that controls a corresponding load by a slave controller that receives a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. A serial load control device comprising: an error detection unit; and controlling to stop the load when a communication error is detected by the communication error detection unit. 2. A serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means; and counting means for counting the number of communication errors detected by the communication error detecting means. When the number of communication errors counted by the counting means exceeds a predetermined number, the load is reduced. A serial load control device that controls to stop. 3. A serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means, counting means for counting the number of communication errors detected by the communication error detecting means, storing means for storing the number of communication errors counted by the counting means in correspondence with the priority in descending order, Extracting means for extracting a priority corresponding to the number of communication errors from the storing means, wherein when the priority is extracted by the extracting means, control is performed so as to stop a load having the extracted priority. negative Load control device. 4. A serial load control device for controlling a corresponding load by a slave controller receiving a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means, counting means for counting the number of communication errors detected by the communication error detecting means, storing means for storing the number of communication errors counted by the counting means in correspondence with the reference priority in descending order, Extracting means for extracting a reference priority corresponding to the number of communication errors from the storing means, wherein when the extracting priority is extracted by the extracting means, a load having a priority equal to or higher than the extracted reference priority is stopped. A serial load control device. 5. A serial load control device that controls a corresponding load by a slave controller that receives a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. A serial load control device comprising: an error detection unit; and resetting the master controller when a communication error is detected by the communication error detection unit. 6. The method according to claim 1, wherein
The serial load control device according to claim 1, wherein said communication error detecting means detects a communication error when the communication error does not recover even after a predetermined time has elapsed since the occurrence of the communication error. 7. A serial load control device that controls a corresponding load by a slave controller that receives a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. A serial load control device comprising: an error detection unit; and when a communication error is detected by the communication error detection unit, a control output to a load is set to a high impedance state. 8. A serial load control device that controls a corresponding load by a slave controller that receives a load control request through serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means; and counting means for counting the number of communication errors detected by the communication error detecting means. When the number of communication errors counted by the counting means exceeds a predetermined number, the load is added to the load. A serial load control device, wherein a control output of the serial load control device is set to a high impedance state. 9. A serial load control device that controls a corresponding load by a slave controller that receives a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means, counting means for counting the number of communication errors detected by the communication error detecting means, storing means for storing the number of communication errors counted by the counting means in correspondence with the priority in descending order, Extracting means for extracting a priority corresponding to the number of communication errors from the storing means, wherein when the priority is extracted by the extracting means, a control output to a load having the extracted priority is set to a high impedance state. Serial load control device. 10. A serial load control device that controls a corresponding load by a slave controller that receives a load control request by serial communication from a master controller, wherein the slave controller detects a communication error with the master controller. Error detecting means, counting means for counting the number of communication errors detected by the communication error detecting means, storing means for storing the number of communication errors counted by the counting means in correspondence with the reference priority in descending order, Extracting means for extracting a reference priority corresponding to the number of communication errors from the storing means, wherein when the extracting means extracts the reference priority, a control output to a load having a priority equal to or higher than the extracted reference priority. In a high impedance state. 11. The communication error detecting means according to claim 7, wherein the communication error detecting means detects the communication error as a communication error if the communication error does not recover within a predetermined time after the occurrence of the communication error. A serial load control device.