JPH0630486B2 - Transmission / reception control method for half-duplex communication - Google Patents

Description

The present invention relates to a transmission / reception control method for half-duplex communication in half-duplex communication, in which the transmission side switches to a reception mode after data transmission and receives a response from the reception side. In particular, the present invention relates to a transmission / reception control method of half-duplex communication that does not miss a response from the receiving side.

Half-duplex communication is when one station is in transmission mode, the other station is in reception mode, and one station sends a message to the other station, and vice versa. Is a communication system in which one station is in a reception mode and a message is transmitted from the other station to the one station to exchange the message. Therefore, when a message is sent from one station to the other, one station must switch to receive mode and the other station must switch to send mode to send a response from the other station. It is necessary to automatically switch the transmission / reception mode after transmission or reception.

[Conventional technology]

For example, in the cluster system shown in FIG.
Many workstations 2 to n are connected to a station controller 1 connected to a host computer,
Station controller 1 and workstation 2
Communication between n is performed by half-duplex communication.

The station controller 1 is a main processor 10
A line controller 11 for connecting to the workstations 2 to n, a channel 12 for a magnetic disk device 14 or a printer 15 which is an external I / O device, a memory 13, and a bus 16 for connecting them. The main processor 10 is configured to perform transmission / reception control according to an interrupt from the line controller 11. On the other hand, each of the workstations 2 to n includes a main processor 21, a line controller 20, a memory (not shown), a channel, and a bus 22. The processor 21 controls transmission / reception in accordance with an interrupt from the line controller 2 like the station controller 1. To do.

[Problems to be solved by the invention]

In such a system, in order to perform half-duplex communication using the station controller 1 as a master station (P station) and the workstation 2 as a dependent station (S station), as shown in FIG. A message (DATA) is transmitted from the controller 1), and the workstation 2 operates to receive a response to the message. That is, in the controller 1, the processor 10 is in the transmission mode and the line controller 11
Reads out a transmission message from the memory 13 via the bus 16 by DMA (Direct Memory Access) and transmits it to the workstation 2. The line controller 11 uses the processor 10 to switch to the reception mode when the transmission is completed.
Is notified of a transmission interrupt, and the processor 10 analyzes this interrupt by a monitor. On the other hand, workstation 2
On the side as well, the line controller 20 detects the reception completion,
The processor 21 is notified of a receive interrupt to switch to the transmit mode, and the processor 21 analyzes this interrupt by the monitor. Then, both processors 10 and 21 execute interrupt processing to switch to the reception mode and the transmission mode, respectively.

Normally, the transmission interrupt process is completed earlier than the reception interrupt process. Therefore, the controller 1 is switched to the reception mode before the workstation 2 is switched to the transmission mode. Therefore, the response from the workstation 2 is normally transmitted to the controller 1. Can be received.

However, the processor 10 of the controller 1
When I / Os such as the magnetic disk 14 and the printer 15 which operate under the control of the processor 10 are connected as shown in FIG. / O may use the bus 16 by the channel 12 to perform DMA or the like. When the bus 16 is used by the I / O operation in this way, the processor 10 cannot use the bus 16 during this time to perform an interrupt process with the line controller 11. Therefore, as shown in FIG. The switching to the reception mode is delayed for t ₁ , and there is a risk that the response from the workstation 2 may be missed, and there is a problem that it is determined that there is no response. This is also the case when transmitting from the workstation 2, and there has been a long-awaited countermeasure for this.

[Means for solving problems]

The present invention provides a transmission / reception control method for half-duplex communication that can prevent missing of a response from a partner station after data transmission in half-duplex communication.

Therefore, according to the present invention, between one station in which a processor, a line controller, and an IO device are connected by a bus, and another station in which a processor and a line controller are connected, one station in a transmission mode is set to a reception mode. In the transmission / reception control method of half-duplex communication in which the one station is switched to the reception mode and the other station is switched to the transmission mode after the data is transmitted to the other station, the transmission from the line controller is performed at the one station. The processor responds to the completion interrupt with the I
When the O device is not using the bus, interrupt processing is performed using the bus to switch to the reception mode, and the processor in the other station responds to the reception completion interrupt from the line controller. A timer is activated so that one of the stations is switched to the transmission mode after a predetermined time has elapsed, which is expected to be switched to the reception mode by the timer.

[Action]

In the present invention, the missing point of the response is prevented by delaying the time point at which the other station in the reception mode switches to the transmission mode by the interruption until the time point at which one station is considered to switch to the reception mode. . Therefore, in the present invention, the other station starts the timer in response to the interrupt, executes the interrupt process after the time monitoring by the timer, and switches to the transmission mode.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, the same components as those shown in FIG. 4 are designated by the same symbols, and 10a and 21a are task control units, which serve as monitors. Those which operate and analyze interrupts, 10b and 21b are transmission control units, and those which perform transmission control according to instructions from the task control units 10a and 21a, 10c and 21c are reception control units, and task control units Receiving control is performed according to instructions from 10a and 21a. Reference numerals 10d and 21d are timer control units, which activate timers by instructions from the receiving control units 10c and 21c and perform timer monitoring.

Each of these units is a block of internal processing executed by the processors 10 and 21.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to the processing flow chart of FIG. 2 and the time chart of FIG.

When the transmission of the above-mentioned message (data) is completed, in the controller 1, a transmission completion interrupt is given from the line controller 11 to the task control unit 10a of the processor 10,
In the workstation 2, the line controller 20 sends a reception completion interrupt to the task control unit 21 of the processor 21.
given to a.

In the controller 1, the task control unit 10a analyzes this interrupt with an interrupt analyzer, and makes the transmission control unit 10b execute post-processing of the transmission interrupt by utilizing the empty space of the bus 16 (FIG. 4).

After finishing the post-processing, the reception control unit 10c is activated to switch to the reception mode.

As mentioned above, if the bus 16 is occupied by another I / O,
During that time, the processing is not executed, the processor 10 is in the stopped state, and the empty space of the bus 16 executes the post-processing with the line controller 11 using the bus 16.

On the other hand, in the workstation 2, the task control unit 21
a analyzes by the interrupt analyzer and causes the reception control unit 21c to execute post-processing of the reception interrupt by utilizing the empty space of the bus 16.

The reception control unit 21c has a timer control unit 21d after finishing the post-processing.
To start the timer.

The timer notifies the task control unit 21a of a timeout interrupt when a predetermined time has elapsed.

As a result, the task control unit 21a analyzes the interrupt with the interrupt analyzer and activates the transmission control unit 21b.
Complete the response return process.

Therefore, the line controller 2 of the workstation 2
A response is sent back from 0 to the controller 1.

Upon completion of this response return, a reception completion interrupt is generated in the controller 1 and the transmission mode is switched to the same as in the step and below, while a transmission completion interrupt is generated in the workstation 2 and the reception mode is switched to in the same manner as the stations and below.

In this way, when one station (controller 1) switches from the transmission mode to the reception mode, the other I / O of the bus 16 is
Even if the switching is delayed due to the occupation by O, the switching to the transmission mode is delayed at the other station (workstation 2) to guarantee the switching delay of the receiving mode at one station,
The response is prevented from being missed by delaying the return of the response.

In the above embodiment, the data transfer from the controller 1 to the workstation 2 has been described, but the same applies to the data transfer from the workstation 2 to the controller 1.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention, and these modifications are not excluded from the present invention.

〔The invention's effect〕

As described above, the present invention has the following effects.

In one station, in response to the transmission completion interrupt from the line controller, the processor performs interrupt processing and switches to the reception mode, and in the other station, the processor starts the timer in response to the reception completion interrupt from the line controller, Since the timer is set to switch to the transmission mode after a predetermined time has passed, I / O
Even if switching to the reception mode is delayed due to the connection of a large number of O's during the I / O operation, it is possible to prevent one station from missing the response, and eliminate the risk of retransmitting it as no response.

While performing half-duplex communication, a large number of I / Os can be connected to a station to perform multiple processing, and the processing capability of the station can be enhanced,
Bus usage rate is improved and processing capacity is also improved.

Since the timer monitoring is a normal interrupt level process, it can be realized without changing the transmission program, and can be realized easily and easily.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a process flow diagram of the configuration of FIG. 1, FIG. 3 is a time chart diagram of the configuration of FIG. 1, and FIG. 4 is a configuration diagram of half-duplex communication. FIG. 5 is an explanatory diagram of transmission / reception mode control in conventional half-duplex communication. In the figure, 1 ... Station controller, 2 to n ... Workstation, 11, 20 ... Line controller, 10, 21 ... Processor, 10a, 21a ... Task control unit, 10d, 21d ... Timer control unit.

Claims (1)

[Claims] 1. A station in a transmission mode between one station in which a processor, a line controller and an IO device are connected by a bus, and another station in which a processor and a line controller are connected, the other station in a reception mode. In the transmission / reception control method of half-duplex communication in which the one station is switched to the reception mode and the other station is switched to the transmission mode after the data is transmitted to the station, the one station transmits the transmission completion interrupt from the line controller. According to the above, when the IO device is not using the bus, the processor uses the bus to perform interrupt processing and switch to the reception mode, and at the other station, reception completion from the line controller is completed. In response to an interrupt, the processor activates a timer, and it is expected that the one station will switch to reception mode. Reception control method of half-duplex communication, characterized in that the switch to transmit mode.