JPS6175427A - Character buffer control system - Google Patents

Abstract

PURPOSE:To carry on communication without any interruption by providing an overflow character buffer to plural circuits in common and storing the overflow character buffer with characters which are received from a circuit where an overflow occurs. CONSTITUTION:Received data from a circuit are set in the character buffer of the circuit through a circuit data control circuit 6 during reception. Characters read out to a readout register 4 with the indication of a character processing control circuit 1 are transferred to a main memory through a character control circuit 7 and a memory transfer control circuit 5. When the load on character processing increases temporarily, the address of a circuit where an overrun occurs is set in an overflow circuit address register 8; and a pointer is set to 0 and the character to which the overrun occurs is set in the byte 0 of the overflow character buffer BFM. Then, characters received successively are stored in bytes 1, 2, and 3 of BFM. When the characters in the overflow character buffer are transferred, the values of the pointer is varied in the order of 0, 1, 2, and 3 to specify bytes of BFM.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for a character buffer provided in a communication control device for temporarily storing data received from a line.

[Conventional technology]

A communication control device generally accommodates multiple lines, assembles the pinto serial reception data sent from the lines into characters and sends them to the host processing device, and vice versa. It decomposes the data into bit serial data and sends it to the line.

During the reception operation, the time when data arrives from the line and the amount of data are generally undefined, so a receive character buffer is provided for each line within the communication control device to deal with fluctuations in traffic. ing.

FIG. 3 is a diagram showing an example of a conventional reception character buffer. In the illustrated example, the character buffer B is 4 bytes for each line with line addresses 0 to N. - has BN.

[Problem that the invention seeks to solve]

In the conventional system, the character buffer that exists for each line has a fixed length, so if an overrun occurs, an error occurs and communication is interrupted.

Such overruns are caused by temporary high loads. In order to prevent this overrun, a method of increasing the character buffer length for each line may be considered, but this would increase the number of buffers by the number of lines, resulting in an increase in the amount of hardware.

Generally, traffic on a communication line is not constant and exists even when there is no communication, and it is not a good idea to provide a large buffer in anticipation of a high traffic situation occurring on all lines at the same time.

[Means for solving problems]

The present invention aims to solve the above problems by adding only a relatively small amount of hardware. To this end, the present invention provides a communication control device that is equipped with a fixed-length line character buffer for each line to store characters received from the line, in which the overflowed characters are stored when the line character buffer overflows. The overflow character buffer is provided in common for multiple lines, and also includes a means for recording the line address where an overflow has occurred, and a pointer for controlling the writing/successive byte position of the overflow character buffer. The characters received from the generated line are stored in the overflow character buffer under the control of the pointer, and
Furthermore, the present invention is characterized in that the reading operation from the overflow character buffer is performed under the control of the pointer.

[For production]

The present invention focuses on the fact that normally only some lines experience high load at a certain point in time.The present invention provides a common overflow character function for multiple lines, and displays received characters from the line where overflow has occurred using this function. It is stored in an overflow character buffer.

〔Example〕

FIG. 2 shows a character buffer in one embodiment according to the present invention.

Character buffer B of 4 bytes for each line from line address O to N. -I have BN. Furthermore, it has a 4-byte overflow character buffer M. Normally, buffer M is not used, but buffer B is provided for each line.

-Communicate using BN. When the character buffer of a certain line among addresses O-N becomes full (fu 11), the next character to be stored is stored in the overflow character buffer M.

FIG. 1 shows a block diagram of essential parts of a communication control device according to an embodiment of the present invention.

In the figure, ■ indicates the type of character processing, and the distinction between sending and receiving.

Line address specification 2 A character processing control circuit that controls the specification of a pointer representing a byte specification of a character buffer. 2 is a character buffer memory consisting of a character buffer BF and an overflow character buffer BFH.

3 is an address creation circuit that creates addresses for character buffers (including overflow character buffers).

4 is a read register in which characters read out from the character buffer memory 2 are temporarily set; 5 is a character buffer B
A memory transfer control circuit when transferring data between P or overflow character buffer BFl,1 and main memory;
Reference numeral 6 denotes a line data control circuit that controls the transfer of data to and from the line; 7 a character control circuit that controls whether the characters read into the read register are output to the main memory or to the line; 8; holds the line address where the overflow occurred (overflow line address register, 9 is a pointer (il) representing the byte designation when writing the BFM, and 10 is the pointer (j) representing the byte designation when reading the BFM. The operation in FIG. 1 is as follows.

During reception, data received from the line is sent to the line data control circuit 6.
to the line's character buffer. Characters successively read out to the read register 4 according to instructions from the character processing control circuit 1 are transferred to the main memory via the character control circuit 7 and the memory transfer control circuit 5. However, if the character processing load temporarily becomes high (or if the character processing load momentarily increases during reception on a high-speed line), the received characters will be buffer-pulled into the character buffer of the line. Overrun may occur.

In such a case, the line address where the overrun occurred is set in the overflow line address register 8, the pointer 19 is set to '0', and the character where the overrun occurred is placed in byte O of the overflow character buffer BFM. . Subsequently accepted characters are bytes t, 2. of BFH.
3 are sequentially stored.

Mainter characters in the overflow character buffer.

・When transferring to memory, set the value of point bJ10 to 0°1.
2. Instead of 3, specify the BFH byte and select the transfer character.

As described above, in the past, line data communication was interrupted due to overrun, but according to the present invention, it is possible to continue communication without overrun.

In the above embodiment, an overflow character buffer BF, an overflow line address register and a pointer i,
Although the configuration has been described in which only one set of j is provided, it is also possible to adopt a configuration in which multiple sets of these are provided.

〔Effect of the invention〕

According to the present invention, even when the line is temporarily in a high load state, it is possible to continue communication by storing received characters in the overflow character buffer. Further, since this overflow character buffer is provided commonly to the line group, the increase in hardware amount can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts of a communication control device according to an embodiment of the present invention, FIG. 2 is a diagram showing a character buffer according to an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a conventional receiving character buffer. FIG. In Figure 1, 2 is a character buffer memory, 8 is an overflow line address register, 9 and 10 pointers, BF
is a character buffer, and BF# is an overflow character buffer. Part 1 Zuka 3

Claims (1)

[Claims] In a communication control device equipped with a fixed-length line character buffer for each line to store characters received from a circuit,
A common overflow character buffer is provided for multiple lines to store the overflowed characters when the line character buffer overflows, a means for recording the line address where the overflow has occurred, and a means for storing the overflow character buffer when the line character buffer overflows. A pointer for controlling write/read byte positions is provided, and characters received from the line where an overflow has occurred are stored in the overflow character buffer under the control of the pointer, and furthermore, the characters are stored in the overflow character buffer under the control of the pointer. A character buffer control method characterized by being configured to read from an overflow character buffer.