JPS62236041A - Error checking system for transmission code - Google Patents

Abstract

PURPOSE:To attain a simple error checking system having high reliability by using the error checking codes BCC for 1-byte character block that is generally used in a computer and converting the code BCC coincident with a transmission control code into a proper 1-byte specific check code to avoid troubles. CONSTITUTION:A microcomputer (A) transfers the transmission characters to a buffer memory 6-2 from a transmission character memory 6-1 and sends them to a BCC calculation part 6-4 at every block. Here an exclusive OR is secured at every digit of characters for blocks for the production of a 1-byte BCC (T). Then a comparison processing part 6-6 compares the BCC (T) with all transmission control codes used. Then the BCC (T) if coincident with the transmission control code is turned into a specific check code and then sent to a data transmission part 7. The part 7 adds the transmission control codes STX and ETX to the front and back sides of a character block together with a BCC or a specific checking code put immediately after the ETX and transmits them to the remote side.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is aimed at solving code errors that occur in data transmission between the two microcomputers when a terminal device of a computer system incorporates two sets of microcomputers. This concerns the checking method.

[Prior Art] As an example of a computer system including a terminal control device to which the present invention is directed, FIG. A terminal device (FAX) 2 is connected, and the information data of the terminal device 2 is arranged by the terminal control device 3 according to a predetermined procedure and transmitted to the electronic exchange 1 via the high-speed transmission control section 4 and the transmission path 5. , is connected to the transmission line of the other party's terminal and transmitted.

Terminal control device rI! , 3 is the main control unit 3-1, which controls the transmission of data to and from the other terminal device, but the operation unit 3 is responsible for specifying the data destination, service type, etc., operating the printer, displaying failures, etc. -2. A microcomputer is used for each of the main control section 3-1 and the operation section 3-2, and necessary data is sent and received between them.

FIG. 4(a) is a diagram showing a functional configuration regarding data transmission between the microcomputers A6 and B8 provided in the main control section 3-1 and the operation section 3-2 in FIG. 3. However, in this case, the information is transmitted from the main control section 3-1 to the operation section 3-2, and the same function is provided in the opposite direction.

In the microcomputer A6, the transmission data is made into byte (8-bit) characters, and a plurality of appropriate characters are grouped together to form a block at position 91, stored in the transmission character memory 6-1, and then stored in the buffer memory 6-1.
Transferred to 2.

In order to transmit this character block to the other party's operation unit, a transmission control code STX (start of block) indicating the beginning and end of each block, ET
X (end of block) is transmission control code generator 6-3
The data is transferred to the data transmitter 7 and added to the block. Furthermore, in order to check errors occurring in each bit within a block on the receiving side, a block check code (BCC) is calculated for each 111th block according to a certain rule in BCCCC calculation-6, and the block check code (BCC) is calculated as follows:
The hexadecimal converter 6-5 converts it into an ASCII code, which will be described later, and adds it immediately after the transmission control code ETX, which becomes a code string and is transmitted from the data transmitter 7 to the other party. For block transmission of data, the transmission and reception control procedures using various transmission control codes, including the setting of the transmission path, are determined.The basics are shown in Figure 4(b), but since they are publicly known, the details are not explained here. Further explanation will be omitted.

Now, the rule for calculating the BCC described in t, which is normally used in computers, is to calculate the exclusive OR of all the characters in the block for each number of digits of each bit of the character, and calculate one byte of BBC. However, when this method is used, there is a possibility that the same one-byte transmission control code as described above will appear. In such a case, not only will the transmission procedure be confused, but there may even be a risk of data errors. 1. BCC, which is used for error checking, can actually become an enemy.

Therefore, in the case of data transmission via a transmission path, conventionally, the BCC is further converted into a 2-byte code.

FIG. 5 shows the number of bits before and after conversion when a conversion method called hexadecimal-ASCII conversion is applied to BCC. Through this conversion, the 1-byte, 8-bit BCC in the -1- column becomes a 2-byte, 16-bit ASCII code in the lower column, and the risk of matching the transmission control code is completely avoided. The BCC-to-hexadecimal converter 6-5 shown in FIG. 4(a) described above is based on this method.

However, when such ASCII conversion is performed using software, in order to convert one hexadecimal character to two characters, it is necessary to process a program using several subroutine steps, which is performed for each block.
Considerable processing time is daytime. Furthermore, the number of bytes increases, so it is not necessarily the best. In particular, in the case of close distances such as between microcomputers in the same terminal equipment, the error rate may be lower than that of a general transmission line with a longer distance. It is desirable to shorten the processing time by using a check method that does not require a check.

[1-1 aspect of the invention] This invention is used for data transmission between microcomputers in terminal devices, etc., in place of the conventional hexadecimal-ASCII conversion described in I- above, and is consistent with the transmission control code. The purpose of the present invention is to provide a simple and reliable block check method that is free from errors and has a short processing time.

[Means for solving the problem] In this invention, the microcomputer A on the transmitting side
Now, take the exclusive OR of the same digits of each bit of the character for each block to create a BCC, compare this BCC with the transmission control code, and if it is the same, write it to a specified 1-byte code other than the transmission control code. Convert it to a check code, leave the different ones as they are without converting them, and add them immediately after ETX at the end of each block. Here, there are at most about 10 types of 1-byte codes used for transmission control, and an appropriate one of the others is specified and used as a check code.

This is referred to as a specific check code.

Microcomputer B on the receiving side calculates the BCC from the received block using the same method as on the transmitting side. Compare this BCC with the transmission control code, convert the same one to the same specific check code as on the sending side, leave the different one as is, and convert these to the received BCC
(including the specific check code), and if they match, it is determined that there is no error, and if they do not match, it is determined that there is a block error.

[Operation] As is clear from the above explanation, in the transmission code error checking method according to the present invention, when the block error checking method (BBC) in the computer is used for data transmission, there is a problem that it coincides with the transmission control code. To avoid this, compare the calculated BCC with the transmission control code,
For the same item, a method is adopted in which another appropriate 1-byte code is specified and converted into a check code. This prevents confusion in the transmission procedure or data errors due to BCC defects.・, will be done.

Here, looking at the processing time of the method according to the present invention, the probability that a 1-byte BCC matches the transmission control code is 256, the total number of possible 8-bit character types.
The ratio of the number of transmission control codes (here, 8) to the number of transmission control codes, that is, only 3%. On the other hand, in the conventional 2-byte ASCII code, all BC
C is converted into 2 bytes, and the number of times it is processed is extremely large. It is only natural that the checking method according to the present invention, which does not require such a large number of processing times, can significantly shorten processing time.

[Embodiment] FIG. 1 is a functional configuration diagram regarding data transmission of two sets of microcomputers A and B to which the transmission code error check method according to the present invention is applied. In this case,
Microcomputer A6 to Microcomputer B
8, and assume that the same function exists in the opposite direction.

The data transmitting section 7 and data receiving section 9 shown in the figure are hardware circuits provided outside the microcomputers A and B as necessary depending on the standards and characteristics of the line 10 to which they are connected.

FIGS. 2(a) and 2(b) are schematic flowchart data for the functions shown in FIG. 1, and the functions will be explained using both figures.

In the microcomputer A, the transmission characters are transferred from the transmission character memory 6-1 to the buffer memory 6-2, and transferred to the BCCCC calculation-6 block by block. Here, an exclusive OR is performed on the block for each digit of the character to create a 1-byte BCC(T). Next, in the comparison processing section 6-6, BCC (
T) is used. All transmission control codes are compared (1), and if there is a match, it is converted to a specific check code (2), and if there is no match, it is transferred to the data transmitter 7 without conversion. In data transmission C-7, from the transmission control code generation section 6-3! j. The obtained transmission control codes STX and ETX are added before and after the character block, and a BCC or specific check code is added immediately after ETX, and the data is sent to the other party. This is repeated (■) until the data to be transmitted ends γ, and then the transmission control code is transmitted (■).

In the microcomputer B, the data received by the data receiving section 9 is written into the buffer memory 8-1, and is also taken into the BCCCC calculation section 2, where BCC(R) is calculated for each block. ■. B C
C(R) is compared with the transmission control code in the comparison processing unit 8-5 in the same way as on the sending side [phase], and if there is a match, it is converted to a specific check code, and the BCC determination unit 8- 4, buffer 1 memory 8-1 to 5. [phase] compared with the received BCC(T) received. Here, if both are equal, then bu...li... 11
(Proceed to check the next block. If they do not match, it is assumed that there is a block error [phase], and r
+) Move to the sending acknowledgment [phase] procedure. On the other hand, when there is no transmission control code that matches the B CC (R) in [phase], the B CC (R) and the received B CC (T) are compared in the BCC determination unit 8-4. Here both are −
- If they match, block error jjj (L); if they do not match, it is assumed that there is a block error [phase], and the same processing as described above is carried out.

All the processing functions described in 1. below can be executed by a software program of a microcomputer. However, if necessary, the hardware circuitry of the data transmitter 7 and the data receiver 9 may be provided outside the microcomputer.

[Effect of the invention] As is clear from the detailed explanation below,
When applying the transmission code error check method according to the present invention to data transmission between microcomputers, a 1-byte character block error check code BCC that is generally used inside a computer is used, and the error check code BCC that matches the transmission control code is used. Appropriate 1 for things
This method avoids trouble by converting the byte into a specific check code, and is a simple yet highly reliable method.

Furthermore, the probability that a 1-byte BCC matches the transmission control code is as small as 3%, whereas with conventional 2-byte ASCII codes, all BCCs are converted into 2-bytes. The effects of the present invention are excellent, such as the processing time required by the method according to the present invention being significantly shortened.

[Brief explanation of drawings]

1 is a functional configuration diagram of a block check method in two sets of microcomputers to which the transmission code error check method according to the present invention is applied; FIG. 2 (aL(b) is a schematic flowchart in FIG. 1; The figure shows an example of the configuration of an electronic switching system having a terminal device to which a conventional transmission code error check method is applied.
FIG. 4(b) is a functional block diagram of the conventional error checking method in data transmission within the terminal device shown in FIG.
FIG. 5 is an explanatory diagram of BCC-hexadecimal ASCII code conversion conventionally used in FIG. 4(a). 1... Electric exchange, 2... Terminal device (FAX)
), 3...Terminal control device, 3-1...Main control unit, 3-2...Operation unit, 4...High-speed transmission control unit, 5...Transmission line, 6...Micro Computer A. 8...Microcomputer B. TODO...Transmission character memory, G-2, 8-1...Buffer memory, 6-3...Transmission control code generation section, G-4, 8-2...BCC calculation section, G-5, 8-3...BCC-hexadecimal conversion unit, G-6,
8-5... Comparison processing unit, 8-4... BCC determination unit,
7...Data transmitter, 9...Data receiver, l
O... line. Figure 2 ((1) Cb) No. 4
Figure (b)

Claims (1)

[Claims] A 1-byte (8-bit) code code representing alphanumeric characters and symbols is used as a character, a plurality of consecutive characters are used as a block unit, and each block unit consists of 1 byte for error detection. block check code (BC
In a transmission method in which data is transmitted between two sets of microcomputers under the control of predetermined transmission control codes (multiple) by adding C), the transmitting microcomputer transmits data in blocks of data to be transmitted. If the bit configuration of the BCC is equivalent to any of the above transmission control codes, it is converted to a 1-byte specific check code that is different from any of the above transmission codes. If the bit configuration of the BCC is different from any of the above transmission control codes, the BCC is transmitted, and the microcomputer on the receiving side calculates the BCC for each received block, and If there is an equivalent in any of the above transmission control codes, it is converted to the specific check code of the sending side, and the specific check code is compared with the transmitted and received BCC to determine whether they match. If the two do not match, it is determined that there is an error, and if the BCC calculated for each received block is different from any of the transmission control codes, the BCC and the transmitted A transmission code error checking method characterized by comparing a received BCC and determining that there is no error when the two match, and determining that there is an error when the two do not match.