JP2008269008A - Serial communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a serial communication device with an error detection means for adding error detection data and detecting errors etc., a retaining means for latching this error information, and a means for initializing the error information of the retaining means during the period when serial communication is not performed, thereby making it possible to initialize the error information without having to provide a means for reporting initialization of the error information. <P>SOLUTION: The serial communication device has an error detection means for adding parity bits and detecting parity errors, etc., a retaining means for latching this error information, and a means for initializing the error information of the retaining means during the period when serial communication is not performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a serial communication system, and more particularly to a serial communication system that performs error detection by adding error detection data.

  There is an image forming apparatus that is connected to a host computer and is divided into a video controller that converts print data sent from the host computer into raster image data, and a printer engine unit that receives the raster image and prints it. A serial communication device is used as a method for transferring raster image data at high speed.

  When the raster image data transferred from the video controller is processed in real time in accordance with the printing speed of the printer engine, even if there is an error in the data, it is not in time to request retransmission of printing. In such a case, data transfer is performed without error detection. In addition, data transfer between the video controller and the printer engine needs to transfer command information from the video controller and status information from the printer engine related to printer control other than video data. Such commands and status information are data related to printer control. When an error occurs, it is desirable to avoid performing control based on the error and avoid malfunction of the printer. As described above, when data transfer that does not require error detection and data transfer that requires error detection are performed by one serial communication device, it is necessary to perform error detection.

  As an error detection method, there is a method of detecting whether or not an error has occurred during communication by adding a parity bit to serial data for transmission and performing a parity check on the reception side.

  As a processing method after error detection, a general-purpose asynchronous transmission / reception circuit that makes an error signal significant when a communication error is detected and a register for storing data at that time are identified, and the state at the time of communication error is identified at the stage of error processing A configuration has been proposed to enable this. (Patent Document 1) In the present invention, the receiving means includes means (reception flag) for notifying the transmitting side of normal reception.

  In addition, a configuration has been proposed in which a reset terminal is provided in an output unit that provides an output corresponding to an error state when a communication error is detected, and the output is held until a reset signal is provided when the error state occurs. (Patent Document 2) In the present invention, it is possible to cancel the holding of the output of the output unit by providing a reset terminal in the receiving means and applying a reset.

In either case, a signal line for notifying an error or canceling the error is required in a system different from the data line for serial communication.
JP-A-8-272719 Japanese Patent Laid-Open No. 10-13384

  However, as described in the background art, when data transfer that does not require error detection and data transfer that requires error detection are performed by one serial communication device, it is necessary to perform error detection. If a means for notifying an error detection from the reception side to the transmission side or a means for notifying the error cancellation from the transmission side to the reception side is provided, there is a problem that the cost increases.

  The present invention has been made in view of the above problems, and performs error cancellation without providing dedicated error cancellation means in a serial communication device that mixes data transfer that does not require error detection and necessary data transfer. It is intended to provide a serial communication device capable of performing the above.

  In order to solve the above-described problem, the invention according to claim 1 is directed to serial data transmission means for adding error detection data to serial data for transmission, serial data reception means for receiving the serial data, and reception. In a serial communication device comprising an error detection means for detecting a data error, an error information holding means for holding the error information, and an initialization means for initializing the error information holding means, serial data is received by the serial data receiving means. And detecting means for detecting that serial data is not transmitted, and the error information initializing means initializes the error information.

  A second aspect of the present invention is the serial communication device according to the first aspect, wherein the error detection data is a parity bit.

  A third aspect of the present invention is the serial communication device according to the first or second aspect, wherein the serial data transmission unit stops clock transmission during a period in which data transmission is not performed. The serial data receiving means detects that the serial data is not transmitted by detecting that the clock transmission is stopped.

  Invention of Claim 4 is a serial communication apparatus of Claims 1 thru | or 2, Comprising: The said serial communication apparatus is a serial communication apparatus provided with an 8B / 10B conversion means, Comprising: Data is a predetermined period, By detecting that the serial data is fixed to HIGH or LOW, it is detected that the serial data is not transmitted.

  According to the present invention, it is possible to perform error cancellation without providing a dedicated error cancellation unit.

  In addition, according to the present invention, it is possible to perform error cancellation without providing dedicated error cancellation means in the clock synchronous serial communication device.

  In addition, according to the present invention, an error can be canceled without providing a dedicated error canceling means in a serial communication device that does not transfer a synchronization clock.

Example 1
Embodiment 1 according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram of a serial communication device according to an embodiment of the present invention. The serial data transmission unit 1 is a parallel-serial conversion unit 2 that converts data to be transmitted into serial data, and adds serial bits to the serial data and transmits the serial data. For example, one parity bit may be added for each 8-bit serial data. The serial data transmitted by the serial data transmitting unit is transmitted to the serial data receiving unit 2 through the data line 3. In synchronization with the data transmission, a serial data synchronization clock is transmitted to the serial data receiving means 5 via the clock line 4. The serial data receiving means 2 can receive serial data by taking in the serial data in synchronization with the clock. The serial / parallel conversion means 6 converts the received serial data with parity bits into parallel data. The parallel data is transmitted to the error detection unit 8 and the data storage unit 9. Of the parallel data, the received data excluding the parity bit is stored in the data storage unit 9 and used as data transmitted by the device control unit 11 at the subsequent stage. The error detection means 8 detects a parity error from the received parallel data with a parity bit. When a parity error is detected, the error detection unit 8 stores the error information in the error information storage unit 10. The device control means 11 can control the device based on the received data and error information.

  FIG. 2 is a timing chart for explaining a method for initializing error information detected as described above. A method for initializing error information will be described with reference to FIGS. The clock line 4 in FIG. 1 has a waveform like the clock in FIG. That is, a clock with a predetermined frequency is output during a period of data transmission, and the clock line is fixed to LOW during a period of no data transmission. When detecting that the clock is fixed to LOW for a predetermined period (for example, a period of 48 clocks) or more, the clock detection unit 7 determines to initialize data transfer. When it is determined that the data transfer is initialized, the clock detection unit clears the error information in the error information storage unit 10. In this embodiment, an example is shown in which the clock is fixed to LOW. However, the clock may be fixed to HIGH.

  In this embodiment, since data transfer is continuously performed and received data is processed in real time, an operation of detecting and retransmitting an error cannot be realized due to time constraints. However, it can be detected that an error has occurred. The error detection result can be used for processing such as redoing data transfer from the beginning when a series of data transfer is completed. In addition, since there is no dedicated signal line for error information initialization, the serial receiver can be initialized with an inexpensive configuration.

(Example 2)
Next, the second embodiment will be described with reference to FIGS. FIG. 3 shows a block diagram of a serial communication apparatus in Embodiment 2 of the present invention. The same numbers as those in FIG. 1 are assigned to the portions described in the first embodiment. The explanation is omitted for these parts. Reference numeral 22 denotes parallel-serial conversion means for converting parallel data into serial data, adding a parity bit, and performing 8B10B conversion. The serial data output from the serial data transmitting unit 1 is received by the serial data receiving unit 2. The serial-parallel conversion means in the serial data receiving means 2 extracts the clock by performing clock data recovery from the serial data converted by 8B10B, and receives the serial data. The received serial data is converted into parallel data and transmitted to the error detection means 8 and the data storage means 9 at the subsequent stage. The subsequent processing is the same as in the first embodiment.

  FIG. 4 is a timing chart for explaining a method for initializing error information detected as described above. In FIG. 4, since the data is 8B10B converted, it is not fixed to HIGH or LOW continuously for a predetermined period (for example, 10 bits) during normal data transmission. In this embodiment, the data line is fixed to LOW during a period when data transmission is not performed. When detecting that the data is fixed to LOW for a predetermined period (for example, a period of 48 clocks) or more, the serial data detection unit 27 determines to initialize the data transfer. When it is determined that the data transfer is initialized, the clock detection unit clears the error information in the error information storage unit 10. In this embodiment, an example is shown in which data is fixed to LOW. However, the data may be fixed to HIGH.

  In this embodiment, it is possible to detect that an error has occurred in a serial communication device that transmits serial data without transmitting a clock. The error detection result can be used for processing such as redoing data transfer from the beginning when a series of data transfer is completed. In addition, since there is no dedicated signal line for error information initialization, the serial receiver can be initialized with an inexpensive configuration.

It is a block diagram which shows the structure of the serial communication apparatus in the 1st Example of this invention. It is a timing chart of the serial communication apparatus in the 1st Example of this invention. It is a block diagram which shows the structure of the serial communication apparatus in the 2nd Example of this invention. It is a timing chart of the serial communication apparatus in the 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Serial data transmission means 2 Parallel serial conversion means 3 Data line 4 Clock line 5 Serial data reception means 6 Serial parallel conversion means 7 Clock detection means 8 Error detection means 9 Received data storage means 10 Error information storage means 11 Equipment control part

Claims (8)

  Serial data transmission means for transmitting error detection data to serial data, serial data reception means for receiving the serial data, error detection means for detecting an error in the received data, and holding the error information In a serial communication device comprising an error information holding means and an initialization means for initializing the error information holding means, the serial communication device comprises a detecting means for detecting that serial data is not transmitted to the serial data receiving means, and the serial data is A serial communication apparatus, wherein the error information initializing means initializes error information upon detecting that no data has been transmitted.   The serial communication device according to claim 1, wherein the error detection data is a parity bit.   The serial data transmission means includes a data synchronization clock transmission means for stopping clock transmission during a period in which data transmission is not performed, and the serial data reception means detects that the clock transmission is stopped. 3. The serial communication device according to claim 1, wherein the serial communication device detects that the serial data is not transmitted.   The serial communication device is a serial communication device including 8B / 10B conversion means, and the serial data is not transmitted by detecting that the data is fixed to HIGH or LOW for a predetermined period. The serial communication device according to claim 1, wherein the serial communication device is detected.   A serial data transmission step for transmitting error detection data added to serial data, a serial data reception step for receiving the serial data, an error detection step for detecting an error in the received data, and holding the error information In a serial communication method comprising an error information holding step and an initialization step for initializing the error information holding step, the serial data receiving step includes a detection step for detecting that serial data is not transmitted, and the serial data is A serial communication method characterized in that the error information initialization step initializes error information upon detecting that no data has been transmitted.   The serial communication method according to claim 5, wherein the error detection data is a parity bit.   The serial data transmission step includes a clock transmission step for data synchronization that stops clock transmission during a period in which data transmission is not performed, and the serial data reception step detects that the clock transmission is stopped. 7. The serial communication method according to claim 5, wherein it is detected that the serial data is not transmitted.   The serial communication method is a serial communication method including an 8B / 10B conversion step, and the serial data is not transmitted by detecting that the data is fixed to HIGH or LOW for a predetermined period. The serial communication device method according to claim 5, wherein the serial communication method is detected.

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