JPH0562492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission control device that transmits and receives digital data signals, and particularly relates to a signal transmission system that enables miniaturization and high reliability of circuits.

[Prior art]

As is well known, in data communication, data is often transmitted using a frame 1 as shown in FIG.

In this figure, 11 is a start delimiter (start flag) indicating the start of a frame, 12 is a destination address indicating a destination station, 13 is an origination address indicating a source station, 14 is a control field containing various control signals,
15 is transmission data, 16 is padding data added when the frame length is extremely short, 17 is a frame check code for code error detection, and 18 is a termination delimiter (termination flag) indicating the end of the frame.
The purpose of adding the padding data 16 here is to prevent problems in transmission control if the transmission data 15 is extremely short, and the padding data 16 is added to avoid code uniqueness. , a signal as close to a random signal as possible is required. Furthermore, as the frame check code 17, an error check code based on the CRC (Cyclic Redundancy Check) method is generally adopted, and an error check code covering the entire transmission signal from the start delimiter 11 to just before the frame check code 17 is calculated. There is a need.

By the way, in conventional devices of this type, the CRC calculation circuit that generates the frame check code 17 and the random code generation circuit that generates the padding data 16 are separate circuits.
This had the disadvantage of increasing the size of the circuit.

[Purpose of the invention]

In view of the above-mentioned circumstances, the present invention provides a signal transmission system that allows circuits to be made smaller and more reliable.

[Features of the invention]

To achieve this objective, the present invention
It is characterized in that the random code (padding data 16) and CRC code (frame check code 17) are generated and transmitted from a digit in the middle of the register string of the arithmetic circuit only by the CRC arithmetic circuit.

〔Example〕

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

FIG. 2 is a block diagram showing the configuration of one embodiment of the present invention, and this is a block diagram showing the configuration of an embodiment of the present invention.
LOCAL NETWORK STANDARDS DRAFT
This is an improvement according to the present invention to the CRC arithmetic circuit for CRC-32 described in "C".
In this figure, numerals 301 to 332 are shift registers each having a length of 1 bit, ◯ indicates an exclusive OR circuit, and ◯ indicates a NOT circuit. Further, 34 is a multiplexer, which is the information data 3 to be transmitted.
1. The CRC calculation result 32 and the random code data 33 are selected and output. That is, the inverter 34 is connected to the data input terminal DO of the multiplexer 34 from the output terminal of the shift register 332.
The CRC operation result 32 is sent to D1 through a, the random code data 33 from the output end of the shift register 316 is sent to D1, and the information data is sent to D2 (this is a general term for destination address 12 to transmission data 15 shown in FIG. 1). ) 31 are supplied respectively, and these are connected to the select end S.
One of them is selected by the selection signal 35 supplied to the terminals 0 and S1, and outputted from the output terminal Q as transmission data 36. In this case, the transmission data 36 is
Exclusive OR is taken with the CRC addition result 32,
As feedback signal 37 for CRC calculation
Supplied to each exclusive OR circuit of the CRC calculation circuit,
CRC calculation is performed.

In such a configuration, when the start delimiter 11 shown in FIG. 1 is transmitted, the information data 31 is selected by the selection signal 35, and the destination address 12
~ Each data of the transmission data 15 is serially transmitted, and in parallel, the above data is transmitted serially.
CRC calculation is performed. In contrast, the selection signal 35 is changed to select the random code data 33,
The necessary length is transmitted as padding data 16, and the CRC calculation is performed at the same time. After transmitting the padding data 16, the selection signal 35 is changed again.
The CRC calculation result 32 is selected and transmitted as the frame check code 17, and finally the termination delimiter 18 is transmitted to complete the transmission of one frame.

According to this embodiment, since the CRC calculation feedback signal 37 consisting of the exclusive OR of the CRC calculation result 32 and the transmission data 36 is not fixed at "0" or "1", the random code data 33 is also A nearly random bit string can be obtained as the padding data 16 without becoming a fixed value. In the above embodiment, the case where the random code data 33 is extracted from the 16th bit has been explained, but the 16th bit is the extraction position.
The same effect can be obtained even if the bit is extracted from any position from the 31st bit to the 31st bit.

〔Effect of the invention〕

As explained above, according to this invention,
Since the CRC calculation circuit is used for both CRC calculation and random code generation at the same time, it is possible to contribute to miniaturization of the transmitting circuit when performing data transmission that requires padding data. In addition, since padding data can be included in the CRC calculation of transmission data, transmission errors can be checked without breaking the standard frame format even when transmitting padding data. It can contribute to high reliability.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the configuration of frame 1;
The figure is a block diagram showing the configuration of a CRC calculation circuit according to an embodiment of the present invention. 16...Padding data (random code),
17...Frame check code, 33...Random code data (signal extracted from a digit in the middle of the register string of the CRC calculation circuit), 301-332...
Shift register (register column).

Claims (1)

[Claims] 1 In a signal transmission method in which a random code is added to data to be transmitted, and a frame check code is added by a CRC calculation circuit before transmission, the above-mentioned
A signal transmission system characterized in that, after transmitting a signal extracted from a digit in the middle of a register string of a CRC calculation circuit as the random code, a frame check code calculated including this random code is transmitted.