JP2006332984A - Communication system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent redundancy of error judgement information from becoming extremely large even when a communication rate becomes relatively low. <P>SOLUTION: A suitable error suppressing method is used for a determined communication rate. For example, an error suppressing method which is relatively simple (i.e. relatively small in redundancy) is selected when the communication rate is relatively low. When the communication rate is relatively high, on the other hand, an error suppressing method which is relatively high in level (i.e. relatively large in redundancy) is selected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to serial communication technology.

  In recent years, communication between a CPU that controls the image forming apparatus main body and a control CPU of an additional apparatus such as a finisher or a paper feed deck is performed by serial communication. In addition, there is an increasing demand for higher speed serial communication. If serial communication is speeded up, errors are likely to occur. Therefore, it is necessary to apply error suppression methods such as parity check and CRC (cyclic redundancy check).

Conventionally, there has been proposed a technique for gradually reducing a communication rate in a transmission device when an error is detected in a reception device (Patent Document 1).
JP-A-6-276252

  However, since the above-described conventional technique uses only a single error suppression method, error determination information (CRC check bits and parity check bits) for suppressing errors as the communication rate is changed may be further redundant. There is.

  In general, the higher the communication rate, the lower the error suppression capability required. Conversely, the higher the communication rate, the higher the error suppression capability required.

  Therefore, in a communication apparatus that supports a plurality of communication rates from high speed to low speed, an error suppression method having a high error suppression capability must be adopted on the basis of the high speed communication rate. In this case, an error suppression method with higher redundancy than necessary is applied to a low-speed communication rate, which causes a decrease in throughput.

  By the way, in the invention described in Patent Document 1 described above, since the communication rate is changed only in a predetermined order, the degree of freedom in changing the communication rate is limited. In addition, if one of the power supplies is turned off during communication, there is a possibility that inconsistency occurs between the communication rates of the two.

  Therefore, an object of the present invention is to solve at least one of such problems and other problems. Other issues can be understood throughout the specification.

  According to the present invention, in a serial communication, an error suppression method suitable for a determined communication rate is used among a plurality of error suppression methods. For example, when the communication rate is relatively low, an error suppression method that is relatively simple (that is, relatively low in redundancy) is selected. On the other hand, when the communication rate is relatively high, a relatively advanced (that is, relatively high redundancy) error suppression method is selected.

  The present invention is a communication system including, for example, a transmission module that performs serial communication and a reception module, and the transmission module determines a communication rate according to the number of error notifications received from the reception module. A determination unit; a selection unit that selects an error suppression method according to the determined communication rate; an adding unit that adds error determination information to data using the selected error suppression method; and the error determination information A data transmission unit for transmitting the added data to the reception module. The receiving module includes a specifying unit that specifies the communication rate based on a signal received from the transmitting module, an error suppression method corresponding to the specified communication rate, and the error determination information received from the transmitting module. And an error detection unit that detects an error in the data received from the transmission module, and an error notification unit that transmits an error notification to the transmission module when the error is detected.

  Furthermore, according to the present invention, the communication rate determined in the transmission module is transmitted to the reception module.

  According to the present invention, since an error suppression method having an accuracy suitable for the determined communication rate is used, the redundancy of the error determination information is extremely increased even when the communication rate is relatively low. There will be nothing.

  Further, according to the present invention, since the communication rate determined in the transmission module is transmitted to the reception module, the communication rate can be changed to a degree of freedom without being limited to a specific order.

  FIG. 1 is a diagram illustrating an example of a communication system according to the embodiment. This serial communication system includes a transmission module 100 and a reception module 150. This serial communication system is employed, for example, as a communication between the control CPU of the image forming apparatus main body and a finisher as a sheet post-processing apparatus connected to the image forming apparatus or a control CPU of a sheet feeding deck as a sheet feeding apparatus. Shall be.

  The transmission module 100 includes a count unit 101 that counts the number of error notifications received from the reception module 150, a communication rate determination unit 102 that determines a communication rate according to the number of error notifications, and a response according to the determined communication rate. A selection unit 103 that selects an error suppression method, an addition unit 104 that generates error determination information using the selected error suppression method and adds the error determination information to transmission target data, and receives transmission target data with error determination information added thereto. A data transmission unit 106 that transmits data to the module 150 is included.

  For example, if the determined communication rate is the first communication rate that is relatively high, the selection unit 103 selects the first error suppression method (eg, CRC method), while the determined communication rate When the second communication rate is lower than the first communication rate, the second error suppression method (eg, parity check method) having a smaller amount of error determination information than the first error suppression method is used. select.

  An adding unit 105 that adds information indicating the determined communication rate (hereinafter referred to as communication rate information) to the transmission target data may be added. In this case, the data transmission unit 106 may transmit the communication rate information in advance as a communication rate signal before transmitting the transmission target data.

  On the other hand, the receiving module 150 extracts a communication rate specifying unit 151 that specifies a communication rate based on the signal received from the transmitting module 150, and extracts data, error determination information, and the like from the received signal according to the specified communication rate. An error detection unit 153 that detects an error in data received from the transmission module 100 using the data extraction unit 152, the error suppression method corresponding to the specified communication rate, and the error determination information received from the transmission module 100, and an error When an error is detected, an error notification unit 154 that transmits an error notification to the transmission module 150 is included.

  The error detection unit 153 includes a first error calculation unit 161 corresponding to the first error suppression method (example: CRC method) and a second error suppression method (example: parity check method). Error calculation unit 162 and a selection unit 163 that selects a calculation result from the first error calculation unit 161 or a calculation result from the second error calculation unit 162 according to the specified communication rate. Also good. Furthermore, the selection unit 163 may function as a comparison unit that detects the presence or absence of an error by comparing the selected calculation result with the received error determination information.

  FIG. 2 is a diagram illustrating an example of a format of a transmission signal according to the embodiment. In this example, the bit length of the header part 201 is 8 bits. The bit length of the address part is also 8 bits. The bit length of the data part is also 8 bits. And the bit length of the parity part 204 which is an example of error determination information is 1 bit. In addition, the arrow in a figure has shown the transmission direction of data. That is, the header part 201 is transmitted first, and then the address part 202 is transmitted.

FIG. 3 is a diagram illustrating another example of the format of the transmission signal according to the embodiment. The parts already described are denoted by the same reference numerals and the description thereof is omitted. Compared to FIG. 2, it can be understood that the parity unit 204 is replaced with a CRC unit 304. The bit length of the CRC unit 304 is 8 bits. Note that the generator polynomial is P (X) = X ⁸ + X ⁴ + X ³ + X ² +1. This generator polynomial is only an example.

  As is apparent from FIGS. 2 and 3, the bit length of the transmission data when the parity check method is selected as the error suppression method is 25 bits (excluding the start bit and stop bit) as a whole, while the CRC is It can be seen that the bit length of the transmission data when selected is 32 bits as a whole. Therefore, in the case of CRC, 1.28 times (= 32/25) of communication time is required compared to the case of parity check.

  FIG. 4 is an exemplary flowchart of a communication method (transmission method) according to the embodiment. In this example, error notifications from the receiving module 150 are counted, and the communication rate when the error count number C exceeds a predetermined number N, that is, when the number of error occurrences exceeds a predetermined threshold N. Change F. Usually, the communication rate is changed to a lower communication rate.

  In step S401, the communication rate determination unit 102 sets the communication rate F to the initial value P0. Usually, the initial value P0 is the fastest communication rate. In step S402, the error notification receiving / counting unit 101 clears the error counter C to zero. In step S <b> 403, the communication rate information adding unit 105 adds communication rate information indicating the determined communication rate F to the head of the header unit 201 or before the header unit 201.

  In step S405, the data transmission unit 106 assembles header content, address content, and transmission target data specified in advance, and creates a transmission data string. In step S406, the error suppression method selection unit 103 compares the determined communication rate F with a preset threshold value regA. If the communication rate F is larger than the predetermined threshold value regA (high speed), the process proceeds to step S406, and the first error suppression method having a relatively large amount of error determination information is selected. On the other hand, when the communication rate F is equal to or lower than the predetermined threshold value regA (low speed), the second error suppression method with a relatively small amount of error determination information is selected.

  In step S408, the error determination information adding unit 104 creates error determination information according to the selected error suppression method. For example, when the CRC method is selected, the error determination information adding unit 104 executes a CRC calculation and sets the calculation result (8 bits) as the error determination information 304. On the other hand, for example, when the parity check method is selected, the error determination information adding unit 104 executes a parity calculation and sets the calculation result (1 bit) as the error determination information 204.

  In step S409, the error determination information adding unit 104 adds the created error determination information to the transmission data string. In step S410, the data transmission unit 106 transmits the header unit 201, the address unit 202, the data unit 203, and the error determination information 204 or 304 in this order.

  In step S <b> 411, the error notification reception / counting unit 101 determines whether an error notification is received from the reception module 150. If received, the process proceeds to step S412, and the value of the error counter C is incremented by one. On the other hand, if no error notification has been received, the process proceeds to step S413.

  In step S413, the error notification receiving / counting unit 101 determines whether or not the communication rate needs to be changed. For example, it is determined whether or not the error counter C exceeds a predetermined threshold value N. If it is necessary to change the communication rate, the process proceeds to step S414, and the communication rate is changed to decrease. On the other hand, if it is not necessary to change the communication rate, the process proceeds to step S415 to determine whether or not to end communication. If the communication is not terminated, the process returns to step S403.

  FIG. 5 is an exemplary flowchart of a communication method (reception method) according to the embodiment. In step S501, the communication rate determination unit 151 specifies the communication rate F based on the header unit 201 (or a signal received before that) received from the transmission module 100, and extracts the specified communication rate F as data. Unit 152 and error detection unit 153 (selection unit 163).

  In step S502, the data extraction unit 152 samples the received signal according to the communication rate F, and extracts the header unit 201, the address unit 202, and the data unit 203, respectively.

  In step S503, the first error calculation unit 161 calculates an expected value (eg, CRC calculation) necessary for error determination based on the first error suppression method (eg, CRC method). In parallel with this, the second error calculation unit 162 calculates an expected value (for example, parity calculation) necessary for error determination based on the second error suppression method (for example, parity check method).

  In step S504, the selection unit 163 compares the specified communication rate F with a preset threshold value regA. If the communication rate F is larger than the predetermined threshold value regA (high speed), the process proceeds to step S505, and an error calculation result by the first error suppression method having a relatively large amount of error determination information is selected. On the other hand, when the communication rate F is equal to or lower than the predetermined threshold value regA (low speed), an error calculation result by the second error suppression method with a relatively small amount of error determination information is selected.

  In step S507, the selection unit 163 compares the selected error calculation result with the received error determination information (204 or 304) to detect an error. If an error is detected, the process proceeds to step S508, and an error notification is transmitted to the transmission module 100. On the other hand, if no error is detected, no error notification is transmitted.

  As described above, according to the present embodiment, since a plurality of error suppression methods that are suitable for the determined communication rate are selected and applied, the communication rate becomes relatively low. However, the redundancy of error determination information does not increase extremely.

  Further, the error detection unit 153 of the reception module 150 is configured so that, for example, the first error calculation unit 161 corresponding to the first error suppression method and the information amount of the error determination information is smaller than the first error suppression method (that is, The second error calculation unit 162 corresponding to the second error suppression method (with low redundancy) and the calculation result from the first error calculation unit 161 or the second error calculation unit 162 according to the specified communication rate If the selection unit 163 that compares the selected calculation result with the error determination information is selected, an error suppression method suitable for the communication rate can be applied even on the receiving side.

  If, for example, a cyclic redundancy check (CRC) method is employed as the first error suppression method and a parity check method is employed as the second error suppression method, for example, the serial error can be reduced with a relatively simple configuration. A communication system can be configured. The parity check method (medium determination accuracy but short determination bit length) and CRC method (high determination accuracy but long determination bit length) are merely examples. It goes without saying that the present invention can be adopted by any other error suppression method.

  Furthermore, the data transmission unit 106 transmits a communication rate signal representing the determined communication rate to the reception module 150, so that the reception module 150 can specify the communication rate more reliably than in the past. As a result, the communication rate can be flexibly changed. For example, assuming that the communication rate for taking is 1 Mbps, 700 kbps, 500 kbps, and 300 kbps, it is possible not only to change from 1 Mbps to 700 kbps, but also to skip 700 kbps and change to 500 kbps or 300 kbps.

  The error notification may be transmitted using a dedicated line different from the data signal communication line. Alternatively, a substantial error notification may be made depending on whether or not the acknowledge signal can be received by the transmission module 100 within a predetermined time without providing a dedicated line. For example, if an acknowledge signal cannot be received within a predetermined time after data transmission, the error counter is incremented by one.

<Communication rate information addition / determination method 1>
FIG. 6 is a diagram illustrating a change example of the signal level on the communication line according to the embodiment. Here, the above-described communication rate information addition method and identification method will be described with reference to FIG. Reference numeral 601 denotes an actual signal level. Reference numeral 602 denotes a corresponding communication state. In the figure, a is a start bit indicating the start of communication. b is a communication rate bit. c is a data start bit representing the start of data. Note that d is a data bit corresponding to the transmission data 203, and the sampling timing of the data is indicated by a solid line arrow. e is an error determination bit corresponding to the error determination information 204 or 304.

  According to the example in the figure, it is assumed that the signal level is always “High” in the non-communication state. Therefore, the reception module 150 starts the reception process by detecting the falling edge (start bit a) of the received signal.

  The communication rate specifying unit 151 of the reception module 150 measures the time interval from the detection of the falling edge of the signal until the signal becomes “High” again by using a timer (not shown), so that the current communication rate is determined. Can be specified. That is, Low portions corresponding to a and b in the figure correspond to the communication rate signal. As for the relationship between the communication rate and the time interval, both the transmission module 100 and the reception module 150 are stored in a memory or the like.

  As described above, the data transmission unit 106 of the transmission module 100 changes the length of the pulse corresponding to the communication rate signal according to the determined communication rate, while the communication rate identification unit 151 of the reception module 150 By measuring the length of this pulse with a timer or the like, the communication rate can be suitably transmitted.

  FIG. 6A shows a case where communication is performed at a certain communication rate (F = P1). On the other hand, FIG. 6B shows a case where the communication rate is reduced by half (F = P1 × 0.5) because errors have occurred more than a predetermined number of times. That is, the pulse width of the communication rate bit b in (B) is twice the pulse width of the communication rate bit b in (A). The communication rate information adding unit 105 described above adds a communication rate bit b corresponding to the communication rate information corresponding to the determined communication rate to the header unit 201. Needless to say, the bit width per information of the data bit d and the error determination bit e also changes as the communication rate changes.

  According to FIG. 6, in both (A) and (B), the transmission module 100 transmits “10110” as the upper 5 bits of the transmission data. Therefore, the reception module 150 extracts “10110” as the upper 5 bits of the data by changing the sampling timing (cycle) according to the pulse width of the communication rate bits.

  As described above, according to the present embodiment, the change of the communication rate can be transmitted by a relatively simple method by changing the length of the pulse corresponding to the communication rate signal according to the determined communication rate. It becomes like this. Therefore, the communication rate can be changed flexibly.

<Communication rate information addition / determination method 2>
FIG. 7 is a diagram illustrating another example of a change in signal level on the communication line according to the embodiment. Note that the same parts as those already described are denoted by the same reference numerals to simplify the description. The method according to FIG. 7 is characterized in that information representing a communication rate is directly embedded in the communication rate bit b. The communication rate bit b is handled as fixed-bit length data that does not depend on the communication rate.

  Specifically, the communication rate bit b is 2 bits long. In FIG. 7A, b = “00”, indicating that the communication rate F is P1. On the other hand, in FIG. 7B, b = “01”, indicating that the communication rate F is P2 (= 0.5 × P1). Although not shown, b = “10” and b = “11” indicate further chastity communication rates.

  Needless to say, the communication rate information may be expressed by using not only two bits but also more bits according to the number of communication rates employed.

  The serial communication system described above can be used not only for image forming apparatuses but also for communication between control circuits inside devices.

    As described above, according to the present embodiment, the data transmission unit 106 changes the communication rate signal content b according to the determined communication rate, thereby changing the communication rate in a relatively simple manner. Can communicate. Therefore, the communication rate can be changed flexibly.

It is a figure which shows an example of the communication system which concerns on embodiment. It is a figure which shows an example of the format of the transmission signal which concerns on embodiment. It is a figure which shows the other example of the format of the transmission signal which concerns on embodiment. 4 is an exemplary flowchart of a communication method (transmission method) according to the embodiment. It is an exemplary flowchart of the communication method (reception method) which concerns on embodiment. It is a figure which shows the example of a change of the signal level on the communication line which concerns on embodiment. It is a figure which shows the other example of a change of the signal level on the communication line which concerns on embodiment.

Claims (10)

A communication system including a transmission module and a reception module for performing serial communication,
The transmission module includes:
A communication rate determining unit that determines a communication rate according to the number of error notifications received from the receiving module;
A selection unit that selects an error suppression method according to the determined communication rate;
An adding unit for adding error determination information to data using the selected error suppression method;
A data transmission unit that transmits the data to which the error determination information is added to the reception module;
The receiving module is
A specifying unit that specifies the communication rate based on a signal received from the transmission module;
Using the error suppression method corresponding to the specified communication rate and the error determination information received from the transmission module, an error detection unit that detects an error in the data received from the transmission module;
A communication system, comprising: an error notification unit that transmits an error notification to the transmission module when the error is detected. The error detection unit of the reception module is
A first error calculation unit corresponding to the first error suppression method;
A second error calculation unit corresponding to a second error suppression method having a smaller amount of error determination information than the first error suppression method;
2. The method according to claim 1, further comprising: a selection unit that selects a calculation result from the first error calculation unit or a calculation result from the second error calculation unit according to the specified communication rate. The communication system described. The selection unit of the transmission module includes:
If the determined communication rate is the first communication rate, select the first error suppression method,
The communication system according to claim 1 or 2, wherein a second error suppression method is selected when the determined communication rate is a second communication rate that is slower than the first communication rate. The first error suppression method is a cyclic redundancy check method,
The communication system according to claim 3, wherein the second error suppression method is a parity check method. The communication system according to claim 1, wherein the data transmission unit transmits a communication rate signal representing the determined communication rate to the reception module. The communication system according to claim 5, wherein the data transmission unit changes a length of a pulse corresponding to the communication rate signal according to the determined communication rate. The communication system according to claim 5, wherein the data transmission unit changes contents of the communication rate signal according to the determined communication rate. A communication method for executing serial communication between a transmission module and a reception module,
In the transmission module,
Determine the communication rate according to the number of error notifications received from the receiving module,
Select an error suppression method according to the determined communication rate,
Add error determination information to the data using the selected error suppression method,
Transmitting the data to which the error determination information is added to the receiving module;
In the receiving module,
Identifying the communication rate based on a signal received from the transmission module;
Using the error suppression method corresponding to the specified communication rate and the error determination information received from the transmission module, detecting an error in the data received from the transmission module,
An error notification is transmitted to the transmission module when the error is detected. A transmitting device that performs serial communication with a receiving device,
A communication rate determining unit that determines a communication rate according to the number of error notifications received from the receiving device;
A selection unit that selects an error suppression method according to the determined communication rate;
An adding unit for adding error determination information to data using the selected error suppression method;
And a data transmission unit that transmits the data to which the error determination information is added to the reception device. A receiving device that performs serial communication with a transmitting device,
A specifying unit that specifies the communication rate based on a signal received from the transmission device;
Using an error suppression method corresponding to the identified communication rate and error determination information received from the transmission device, an error detection unit that detects an error in data received from the transmission device;
An error notification unit that transmits an error notification to the transmission device when the error is detected.

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