JPS58221540A - Data communication system having relay bus - Google Patents

Abstract

PURPOSE:To perform the bus relaying with a small dalay caused by buffer, by displaying an input every time the length of the data which is buffed by a receiver buffer exceeds a prescribed level, then transmitting the data in the buffer at a speed coincident with a communication system. CONSTITUTION:A sending buffer BFCa of an adaptor 3 buffs the communication frame fed from a communication system 1, and a receiver displays the data in the buffer every time this data has a prescribed length T0 equal to one-to- integer of the communication frame. Then the data of length T0 is transmitted to a relaying bus 5 via a transmitter T. The data given from the bus 5 is buffed by the receiver R of an adaptor 4 and then displayed every time the data exceeds the length T0. The transmitter T transmits the data in the buffer to a communication system 2 of the receiving side in response to the communication speed as long as the data is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a data communication system having a relay bus.

In order to form a wide-area data communication system by interconnecting a plurality of data communication systems existing in different regions, the data communication systems are connected by a relay bus.

The conceptual configuration of such a wide area communication system is as shown in FIG. 1. Communication systems 1 and 2 are connected to a relay bus 5 by adapters 3 and 4, respectively, Allowing them to communicate with each other. Each of the adapters 3 and 4 has two systems of buffer and control circuits (hereinafter simply referred to as buffers) BFCa and BFCb, and a receiver R and a transmitter T respectively attached to these buffers. One of the two buffers 1, BFCa, is a send buffer that transmits data from the communication system to the relay bus 5, and the other buffer 'BFCb is a receive buffer 1, which receives data from the relay bus 5 and transmits it to the communication system. be.

In such a communication system, when the communication system 1 on the transmitting side, for example, provides one frame of communication data to the relay bus 5 through the adapter 3, this communication frame is transmitted through the relay bus 5 and sent to the communication system through the adapter 4. Sent to 2.

At this time, the communication system 2 that receives the data needs to be given one communication frame of data consecutively in order to receive the data correctly.

For this reason, conventionally, when sending data from the communication system 1 to the relay bus 5, the entirety of one communication frame is stored in the -H send buffer BFCa, and the 1 communication frame stored in this send buffer IBFca is The frame data was sent to the relay bus 5. However, in this case, a communication delay occurs by the theoretical length T of one communication frame. The relay bus 5 is designed to be sufficiently high-speed so that its presence does not affect the operation of the communication system connected to it. If a delay occurs, it is inconvenient because the effect of increasing the speed of the relay bus is diminished.

An object of the present invention is to provide a data communication system control method having a relay bus with small communication delays due to buffers.

In the present invention, a plurality of separate communication systems are connected by a relay bus whose communication speed is higher than the communication speed of the communication systems, and a send buffer is provided between each communication system and the relay bus from the communication system to the relay bus. In a data communication system having a relay bus, which is provided with a receive buffer that goes from the relay bus to the communication system, the send buffer receives the communication frame given from the communication system by ringing the communication frame from the communication system, and The data is an integer fraction of the communication frame.
data input means for displaying the data each time a predetermined length TO is reached, and data of length TO in the buffer within a data output period TS (<TO) that starts after the display of this data input means occurs. The receive buffer has a data output means for transmitting the data to the relay bus, and a data input means for buffering the data given from the relay bus and displaying it each time the length of the data in the buffer exceeds TO. and data output means for transmitting the data in the buffer 1 to the communication system at a speed matching the communication speed on the condition that the display of the data input means has occurred. The above objectives have been achieved by a data communication system having the following.

The following is real, /i! The invention will now be described in detail by way of example.

The present invention utilizes the send buffer y of adapter 2.3 in FIG.
The input/output control means for BFca and receive buffer BFCb are improved, and the following control means are provided for each.

First, the send buffer BFCa is provided with data input means and data output means that operate independently. The data input means prepares the data each time it buffers the data of one communication frame given from the transmission side communication system by a predetermined length TO (=T/N N: integer) shorter than the frame length T. The data output means has a function of displaying completion, and the data output means has a function of transmitting the data of length TO that is ready in the buffer to the relay bus 5 at a constant period S according to the communication speed. be made to have. The transmission period Ts is the length in the buffer TO
The value is chosen to be sufficient to completely transmit the data. As the relay bus 5, a bus whose communication speed is faster than the communication speed of the transmitting side communication system is used.
It is very difficult.

Receive buffer BFCb is also provided with data input means and data output means that operate independently. Come on...
The data input means has a function of buffering the data received from the relay bus 5 and displaying a data preparation completion signal every time the length of this buffered data exceeds To. After the ready signal is issued, the f-event in buffer 1 is sent to the communication system on the receiving side.
It will have a function to send data according to the communication speed. Communication systems 1 and 2 are assumed to have the same or similar communication speeds.

Send buffer rBFca and receive buffer rB
The functions of such input/output means in the Fcb can be realized by a microprocessor or appropriate firmware.

Send buffer BFCa and receive buffer [3F
By using the Cb restriction means in this way, communication between the two communication systems is performed as follows. An explanatory diagram of the operation is shown in FIG. In FIG. 3, A, B, and C indicate various transmission timings of the communication system on the transmitting side with respect to the transmission period S of the relay bus 5.

Now, suppose that the communication system 1 transmits a communication frame of length T to the communication system 2, the data input means of the cent buffer BFCa of the adapter 3 buffers the received data, and the length is When the time reaches 7o, data preparation completion is displayed, and subsequent input data is buffered.

After the data preparation completion display is displayed, the data output means
At the start of the transmission cycle TS of the relay bus 5, the transmission of the buffered data 11 of length TO is started. Between the data preparation completion display and the beginning of the cycle TS, time variations occur as shown in A, B, and C depending on the timing difference.

A means that the period Ts starts immediately after the data ready indication, and B means that the cycle II Ts starts immediately before the data ready indication.
begins, then C is an intermediate case between those two cases.

First, to explain case A, the data output means starts transmitting the first data (1) immediately after it is prepared, and completes the Ts waiting time transmission. When this is completed, the buffering of the next data I2 of length TO has not yet been completed in the buffer, so the data preparation completion indication does not appear.

Therefore, the data output means does not transmit data in the next cycle.

The first data 11 sent by the adapter 3 is transferred to the relay bus 5.
The signal is applied to the receive buffer 7BFCb of the adapter 4 through the data input means, and buffered by the data input means.

In the adapter 3, buffering of the data I2 is eventually completed, and a data preparation completion display is generated accordingly. Then, the data output means has a transmission period of '7-s.
This data 2 is transmitted at the beginning of , and is buffered in the receive buffer BFCb of the adapter 4.

Similarly, the adapter 3 inputs and outputs communication data.

When data I2 is buffered in adapter 4,
Since the buffered data length exceeds TO, the data input means displays data preparation completion. Then, the data output means transmits the buffered data to the communication system 2 from the beginning thereof. Therefore, this causes the first data 11 to be transmitted to the communication system 2.

When the data output means finishes transmitting the data It at time 11TO, the data manual means transmits the next data ■2 at time TS.
Since the data has been prepared in the buffer, the completion indication has already been generated, and the data output means continues to transmit the next data I2 accordingly. If the relationship between TO and S is appropriately selected, preparation for the next data is always completed in the buffer while one data is being transmitted, so that the transmission data can be transmitted without interruption for one frame.

At this time, the delay time until communication data from the communication system 1 reaches the communication system 2 is Ta. This delay time Ta has a smaller value than the communication frame length T.

The same operation as above is performed in cases B and C, but the difference in timing causes a difference in delay time. In case B, the phase of the data transmission cycle TS is slightly ahead of that in case A, so the delay time is Tb, which is slightly shorter than in case B. In the case of C, since the phase of the period Ts is further advanced, the delay time becomes Tc, which is even shorter.

In the end, case A has the largest delay, and the delay is TO+2'T'8. Here, since Ts<TO, this delay does not exceed 3To.

Furthermore, since TO=T/N, the delay time can be made sufficiently smaller than the communication frame length T by choosing N to be large.

Furthermore, in the adapters 2 and 3, it is not necessary to buffer all of the communication frames, so the capacity of the buffers is also reduced. Regarding the capacity of the buffer T, in case B, since the timing of data transmission from the adapter 3 to the relay bus 5 is the slowest, the largest amount of data is buffered in the send buffer FBFQa at this time.

Therefore, the maximum buffer capacity is required at this time, and the capacity is TO+TS. This is sufficiently smaller than the conventionally required buffer capacity IT.

Although the present invention has been described above with reference to preferred embodiments, the present invention may have various embodiments within the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a conceptual configuration diagram of a data communication system having a relay bus to which the present invention is applied, FIG. 2 is a buffer status diagram in the conventional case, and FIG. 3 is an explanatory diagram of communication execution according to the present invention. , FIG. 4 is a state diagram of the buffer in the present invention. 1.2... Communication system, 3.4... Adapter, 5
...Relay bus, BFCa...Send buffer, B
FCb...Receive~・Buffer 1, R...Receiver,
■・・・Transmitter

Claims (1)

[Claims] A plurality of separate communication systems are connected by a relay bus having a communication speed higher than the communication speed of the communication systems, and between each communication system and the relay bus, there is a connection between the communication systems and the relay bus. In a data communication system that has a relay bus that is provided with a send buffer door and a receive buffer that goes from the relay bus toward the communication system, the send buffer receives communication frames given from the communication system from buffer 1. The data in the ring buffer is an integer fraction of the communication frame.
data input means for displaying the data each time a predetermined length To is reached, and data of length To in the buffer within a data output period Ts (<To) that starts after the display of this data manual means occurs. The receive buffer has a data output stage that sends the data to the relay bus, and the receive buffer has a data input stage that buffers the data given from the relay bus and displays it every time the length of the data in the buffer exceeds To. and data output means for transmitting data in the buffer at a speed matching the communication speed of the communication system on the condition that an indication of the data input means has occurred. Data communication system.