JPS61283952A - Data transfer instrument - Google Patents

Abstract

PURPOSE:To obtain a data transfer instrument having the high transfer efficiency by using an idle amount detecting means and a transfer data control means which decides whether or not the data should be transferred to a detected buffer memory and therefore eliminating the undesired retransmission and waiting time of data. CONSTITUTION:An instrument A at the transmitter side contains a data transfer means 1A which transfer data to a buffer memory 1B provided to a instrument B at the receiver side and a transfer data control means 2A which controls the quantity of data sent by the means 1A. While the instrument B includes a buffer memory 1B which stores temporarily the data given from the device A and an idle amount detecting means 2B which detects the idle amount E of the memory 1B. A transfer data control means 2A compares the quantity of information to be transferred with the amount E and delivers a command for transmission of information when the amount E is sufficient for transmission of information.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a buffer memory provided in a receiving device, which divides data of an amount whose maximum value is specified according to a certain procedure from a transmitting device at any time. The present invention relates to a data transfer device for transferring data to a computer.

[Conventional technology]

FIG. 3 is a diagram showing the concept of data transfer by a conventional data transfer device. The conditions in the figure are described below.

Data transfer takes place between device A and device 8. In this figure, transfer of a data block from device A to device B is taken as an example.

As a command between device A and device 8, POLL is a command for checking the status of the other device.

DBn (n=1.2...) is a data block.

ACK, BUSY, and REPRY are response commands from the partner device. The buffer memory from device B is endlessly controlled. In other words, a write address counter WC and a read address counter RC exist independently, and the write address counter WC is incremented each time 7 blocks of data are received, and the read address counter RC is used to count up data each time a 7-lock data is received. The count is incremented each time it is sewn and processed. The buffer size of the buffer memory is assumed to be N, and the response to device A is determined as a READY response when the free space E is more than half the buffer size N.

Next, the operation will be explained. When receiving the command POLL from device A in the initial state, device B responds with an ACK because the free space E is greater than or equal to size N/2. Then, device A determines that data block transmission is possible, and transmits the first data block D'B1 (data amount N/8). When device B finishes receiving the data block DBI, the write address counter WC is at N/8, and the free space E in the buffer memory is 7N/8, so it makes an ACK response, and then enters processing operation and writes the read address. Counter RC is incremented sequentially.

Device A sends an ACK in response to the data block DBI transmission.
, the next Data Pro Tsuta DB2 (4N
/8) is sent. Device B receives the data block DB2, performs a writing operation to the buffer memory, and also performs a processing operation. Then, when the write address counter WC is at 5N/8 and the read 7 address counter RC is at 0.5N/8 at the end of reception of data block DB2, the buffer memory free space E=size 3 .5N
/8, so a BUSY response is made. This BUSY is device A
This means that the free space is insufficient for the size 4N/8 at the end of the previously sent data block. Then, device A executes command P until an ACK response is returned from device fB.
Send OLL to check. Time t1 in the figure is the period in which "BUSY" is returned in response to the command POLL.

During this time t1, the processing operation progresses in device B, and when the free space in the buffer memory reaches E=4N/8, an ACK response is issued.

Then, device A stores the next data block DB3 (5N/8
) starts sending. On the device B side, when the write address counter WC overlaps the read address counter RC, the REPRY bit is set, and thereafter the data in the data block DB3 is discarded.

Then, since there is a REPLY bit at the end, device A
A REPLY response is made to the request. Then, the write address counter WC is returned to its original position.

When device A receives a REPLY response, it determines that the previously sent data block has been discarded midway through, and prepares for retransmission. Then send command P'OLL and ACK
If yes, retransmission of data block DB3 (5N-8) is started.

When all data blocks DB3 are received, the free space in the buffer memory is E-0,8N/8, so device B
Continue the USY response for t2.

Then, when there is an ACK response from device B, the device starts transmitting the next data block DB4 (<0.5N/8) [Problem to be solved by the invention] The conventional data transfer device is configured as described above. □This reduces the efficiency of the overall processing within the sending device, such as retransmission of data blocks and waiting time even though shorter data blocks are ready to be received by the sending device. was. ``This invention was made to solve the problems mentioned above, such as unnecessary retransmission of data.

The purpose is to obtain an efficient data transfer device by eliminating waiting time.

[Means for solving problems]

Therefore, the data transfer device according to the present invention includes a free space detection means for detecting the free space of the buffer memory on the receiving side, and a data transfer device that detects the free space in the buffer memory based on the information on the free space in the buffer memory detected by the free space detection means. The present invention is characterized in that it includes a transfer data control means for determining whether or not to transfer data to the memory.

[Operation] The free space detection means provided in the receiving side device detects the free space in the receiving side buffer memory, and sends information on this free space to the receiving side device.

The transfer data control means provided in the sending device compares the free space information with the amount of information to be sent, and if the former is larger than the latter, transfers the data to the buffer memory provided in the receiving device. .

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1(A) is a block diagram of a data transfer device according to the present invention.

In the figure, a device A on the sending side includes a data transfer means IA for transferring data to a buffer memory IB provided in a device B on the receiving side, and a transfer means IA for controlling the amount of data sent by the data transfer means IA. Two data control means are provided. Also, the receiving device B has the sending device A.
A buffer memory IB for temporarily storing data sent from the buffer memory IB and a free space detecting means 2B for detecting the free space E of the buffer memory IB are provided. The transfer data control means 2A compares the amount of information to be transferred with the free space in the buffer memory IB, and when the free space is sufficient to transfer the information, issues a command to transfer the information.

Next, the operation of the data transfer device is explained by the first section indicating the transfer state.
This will be explained with reference to the explanatory diagram in FIG.

In FIG. 1(B), in the initial state, device B is
When the LL command is received, the buffer memory free space E
is calculated by the free space detection means 2B and set in the ACK command.

In this case, the size of the free space E of the buffer memory is N. Then, since device A calculates by itself that the next data block DBI will be of size N/8, it compares this data block DBI with the free space E and determines that data block DBI (N/8) can be transmitted. It is determined that it is, and the transmission begins. At the end of receiving DBI (N/8), device B calculates the buffer free space E and sets it in the ACK command.

In this case, the size of the buffer memory free space E is 7N/
It is 8. Next, data block DB2 (4N/8) is sent. The ACK for this data block DB2 (4N/8) has a size of 3.5N/8. Then, the transfer data control means 2A of the device A instructs to temporarily suspend the transmission since the data block DB3 to be transmitted next has a size of 5N/8. Temporary hold means waiting until device B becomes ready to receive data block DB3 (5N/8).

This is sending a POLL command and ACK in response.
By checking the contents of the command. Then, when the ACK becomes larger than the size 5N/8, data block DB3
Start transmitting (5N/8). The same process will be performed thereafter.

FIG. 2 is a flowchart showing the control of the transmitting side device A and the receiving side device B for carrying out the above control.

Since the explanation of this figure overlaps with the explanation of FIG. 1, it will be omitted.

In the above embodiment, it was explained that the transmission of the ACK command from the receiving device B occurs in response to the transmission of the POLL command or data block from the transmitting device A, but the present invention is based on the basic data transfer protocol. The main purpose of this is not to control the amount of free space in the receiving device B, but to notify the transmitting device A of the free space on the receiving device B.

〔Effect of the invention〕

As explained above, the data transfer device according to the present invention compares the free space in the buffer memory detected by the free space detection means with the amount of information to be transferred, and based on the comparison result, transfers data to the buffer memory or not. Since it is determined whether or not the data is transferred, data can be transferred depending on the state of the receiving device, eliminating waiting time when transferring data and providing an effective data transfer device.

[Brief explanation of drawings]

FIG. 1(A) is an overall block diagram showing an embodiment of the present invention, FIG. 1(B) is an explanatory diagram of data transfer, FIG. 2 is a flowchart showing the flow of data transfer, and FIG. FIG. 2 is an explanatory diagram of conventional data transfer. IA: Data transfer means, IB: Vanor memory, 2A: Transfer data control means, 2B: Free space detection means. Agent Masuo Oiwa (2 people) = 11-

Claims (1)

[Claims] Detects the free space in the buffer memory on the receiving side in a data transfer device that divides the amount of data with a specified maximum value from the sending device according to a certain procedure and transfers it to the buffer memory provided in the receiving device. The buffer memory free space detected by the free space detection means is compared with the amount of information to be transferred, and based on the comparison result, it is determined whether or not to transfer data to the buffer memory. What is claimed is: 1. A data transfer device comprising: transfer data control means.