JPH01312656A - Control device for receiving buffer - Google Patents

Abstract

PURPOSE:To enable a high speed operation by selecting a block in which received data is written and reading out data from the selected block by referring to a first flag and a second flag. CONSTITUTION:The block in which the received data is to be written can be selected, and the presence of the received data can be known by seeing the first flag 11. Beside, both processing to write the received data in the block in turn and the processing to read out the data in turn come possible by referring to the second flag 12. The write of the received data and the read of the data can be executed by a block unit by using these flags 11, 12, and simultaneously, flow control can be executed. Thus, the high speed processing comes possible and the flow control is made simple compared with a customary system to process the data by every one byte.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a reception buffer for storing data from the outside, which is commonly used in systems that use data from an external system, such as data communications.

[Summary of the invention]

In this invention, the receive buffer is divided into a plurality of blocks, and associated with the receive buffer are a first flag indicating whether each of the blocks is occupied and a second flag indicating the block to which the received data is to be written next. 2 flags and
Next, a third flag indicating the block from which the data is to be read and a fourth flag indicating whether the block will overflow are formed, and the received data is written with reference to the first flag and the second flag. The received data is written to the selected block, and the first flag and the third block are selected.
A block is selected from which stored data is to be read by referring to the flag, and data is read from the selected block, thereby writing received data and reading data in block units. Flow control becomes simple and high-speed operation is possible.

[Prior Art] In data communication, a receive buffer is provided to temporarily store received data. As one of the conventional receive buffers,
A ring buffer is known in which a buffer memory is considered to have a ring configuration. The ring buffer is configured to form a write pointer corresponding to a write address and a read pointer corresponding to a read address, and perform flow control using both pointers. The advantage of the ring buffer is that the buffer capacity can be virtually always equal to the buffer capacity.

[Problem to be solved by the invention]

Although ring buffers seem to utilize memory as efficiently as possible, they suffer from the following drawbacks.

First, it is inefficient because data is extracted from the received bytes one byte at a time.

Second, the number of usable bytes remaining from the received bytes is calculated each time (one byte at a time) to perform flow control. Therefore, it is not only inefficient, but also increases overhead and does not allow high speed data retrieval.

Therefore, an object of the present invention is to provide a received byte control device that is efficient and capable of high-speed operation.

[Means to solve the problem]

In this invention, the receive buffer is divided into a plurality of blocks, and each of the blocks has a first flag indicating whether it is occupied or not, a second flag indicating the block to which the received data is to be written next, and a second flag indicating whether the received data is to be written next. A third flag indicating the block from which the data is to be read and a fourth flag indicating whether the block overflows are formed, and the block to which the received data is written with reference to the first flag and the second flag. is selected, the received data is written to the selected block, and the first flag and the third
A block from which stored data is to be read is selected with reference to the flag, and data is read from the selected block.

[Operation] By looking at the first flag, it is possible to select a block to write received data or to know whether there is received data. Further, by referring to the second flag, it becomes possible to sequentially write received data into blocks and sequentially read data. Using these flags, it is possible to write received data and read data in block units, as well as perform flow control. Therefore, compared to the conventional method of processing one byte at a time, high-speed processing is possible and flow control is simpler.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a system to which the present invention can be applied. In FIG. 1, reference numeral 1 indicates a received data processing block to which external data 2, such as serial data, is supplied. This reception data processing block 1 is provided with a reception byte, and data 2 from the outside is received and passed to the application block 3 through the reception data processing block 1. Specifically, the received data processing block 1:
It operates on interrupt processing, and the application block is
It works in the main program.

FIG. 2 shows the configuration and flags of the receive buffer. The receive buffer is divided into n blocks of m bytes each. Therefore, the capacity of the receive buffer is (mXn bytes). For example (m=2 bytes, n=8, mXn=16
part-time job).

A first flag-fourth flag is generated in conjunction with the receive buffer.

The first flag is an n-bit (8-bit) active block flag 11, which is an active block flag 1.
1 is used to determine which block is in use.

By looking at the active block flag 11, it can be determined whether each block is occupied. Each bit of the active block flag 11 is 1, which indicates that it is in use (that is, data has not been read after it has been written), and 0, which indicates that it is in use (that is, data has not been read after being written).
” indicates that the block is not in use (the written data has been read to the application block 3, but no data has been written after that). Data is written to the block whose active block flag 11 is “0”. Furthermore, it can be determined from the active block flag 11 whether there is data in the reception buffer.

The second flag is a 3-bit current active receive block 12, which indicates the block currently being received within the interrupt program, from which the next block to write data can be determined.

The third flag is a 3-bit current active application block 13 indicating which block is currently being used to pass to application block 3 within the main program. This current active application
The block to be read next can be determined from the silon block 13.

The fourth flag is a data byte number flag 14 corresponding to each of the eight blocks, and a data byte number flag 1.
4 indicates the number of bytes of data stored in each block (up to 2 bytes). By looking at this data byte number flag 14, it is possible to detect a risk of overflow in units of blocks.

Furthermore, as a control signal for flow control,
ON and X0FF are used. When XON is sent, it means that reception is possible, and when X OFF is sent, it means that reception is stopped because there is no memory available.

Using the above flags, received data processing and application block processing are performed in block units.

Referring to FIG. 3, the received data processing operation executed by the interrupt subroutine program will be described.

First, in step ■, the flow control control signal
It is checked whether ON is being sent. When there is no XON, reception is not possible, and when there is XON, reception is possible. If it is determined that the data can be received, the process moves to step (3) and the current receive block (the block in which the received data is written) is selected. This selection is made with reference to the active block flag 11 (first flag) and the current active receive block 12 (second flag), and received data is written to the unused block. Additionally, the active block flag 11 is changed, and the current active receive block 12 is set to correspond to the selected block.
Next, the received data is stored for the selected block (Ste knob ■).

Next, the data byte count flag 14 (fourth flag) indicates whether the block in which the received data is stored is full.
You can find out from (Ste Nobu ■).

If it is -, move to step ■, and check whether the remaining blocks are 1 or less by checking the active block flag 1.
You can check from state 1. If the number of remaining blocks is 1 or less, there is a risk of overflow, so
Send FF (step ■).

Referring to FIG. 4, data transfer to the application block running in the main subroutine program will be explained.

In the first step (2), it is checked with reference to the active block flag 11 whether there is any received data. The block with received data is selected as the current active application block (step o), and the received data of this selected block is transferred to the application block 3 (step @).

Next, in step [phase], it is checked whether the remaining blocks are 1 or less. If it is not less than 1, it is checked whether X0FF is being sent (step 0).

When X OFF is being transmitted, a control signal X0N (meaning that it can be received) is transmitted (step 2).

Note that the flowcharts shown in FIGS. 3 and 4 are examples, and can be modified depending on the application.

〔Effect of the invention〕

In this invention, since the receive buffer is divided into blocks, it is possible to easily separate the operation of storing data from the external interface to the receive buffer and the operation of passing data from the receive buffer to the application block. Data input/output can be performed in blocks, increasing speed.

Furthermore, the usage status of the receive buffer can be determined simply by preparing an active block flag corresponding to each block of the receive buffer, so the flow control algorithm can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the outline of a system to which this invention can be applied, Fig. 2 is a route diagram used to explain the configuration of the reception buffer and flags, and Figs. 3 and 4 are explanations of one embodiment of the invention. This is a flowchart used for. Explanation of main symbols in the drawings 11: Near active block flag, 12: Current active receiver block, 1
3: Current active application block, 14: Data byte count flag. Agent Patent Attorney Tadashi Sugiura
2< h゛ ・, t agt t t ) Fig. 2 ( /2 ゛ ku〈 ＼ ) O-thousand eat
70-+ Yard HA-

Claims (1)

[Claims] A reception buffer is divided into a plurality of blocks, and a first flag indicating whether each of the blocks is occupied, and a second flag indicating a block to which received data is to be written next. , a third flag indicating the block from which data is to be read next and a fourth flag indicating whether said block overflows are formed, with reference to said first flag and said second flag. A block into which the received data is to be written is selected, the received data is written into the selected block, and a block from which the stored data is to be read is selected by referring to the first flag and the third flag. . A receiving buffer control device, wherein data is read from the selected block.