JPH0636500B2 - Polling control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] An efficient polling control method when all polling destination devices are unresponsive at system startup, etc., and minimize polling reception delay at system startup etc. For the purpose of
When polling is performed in a specified order, if a polling delay factor such as no response retry to polling occurs in a polling destination device, a certain polling delay is set and the polling for the device is thinned during that period In the polling control method in which the influence on the polling device is reduced, the polling delay is ignored and the polling is performed when the polling delay factor is generated in all of the plurality of polling destination devices.

[Industrial application field]

The present invention relates to a polling control method in a system for performing data communication with a plurality of devices connected via a transmission line, and particularly when polling destination devices are all in a polling delay state when the system is started up. In case of efficient polling control method.

[Conventional technology]

A conventional polling control system will be described with reference to FIG. FIG. 4 shows a sequence example when the polling source device P performs polling on two polling targets A and B.

The polling source device P sequentially sends polling signals Pol (A) and Pol (B) to the polling destination devices A and B. In this example, the polling source device P is started up first, and at the time of starting the polling operation, the polling destination devices A and B are in a not-ready (communication response unavailable) state because the power is not turned on or the polling reception is rejected. It is supposed to be in.

First, the device P sends Pol (A) to the device A, but since the device A is in the not-ready state, there is no response. Therefore, the device P executes the retry several times and becomes the retry out.

The device P sets a polling delay time T for the device A that has been retried out, and thins out polling for the device A until the time T elapses.

This is because there is a high possibility that a device that has been retried out will be retried again with no response even in the polling of the next sequence, so the polling cycle of other devices that can respond to polling will be degraded. It is done to prevent it.

Subsequently, the device P sends Pol (B) to the device B. At this time, the device B is also in the not-ready state, so after several retries, it is retried out. Therefore, the device P sets the polling delay T, and the device B
The next sequence of polls for is not done for time T.

When the device A becomes ready within the previous polling delay time T for the device A, Pol (A) is sent after the time T ends, and the device A returns a response (A).

After that, while the polling delay T for the device B is valid as indicated by, only Pol (A) is sent to the device A, and the response from the device A is returned for each.

Then, the polling delay T for the device B is completed and the devices B and Pol (B) are transmitted from the device P, but a retry is performed because of no response, and the polling delay T is set again due to retry out. .

Therefore, as in the case of the following or the above, only the transmission and response of Pol (A) to the device A are performed.

FIG. 5 is a flow chart showing the polling control procedure in the polling source device P described above. The upper half of the flow in the figure is the procedure for the polling destination device A, and the content of each procedure is the same.

Explaining only the procedure for the polling destination device A, at the start of polling, it is first determined whether or not the device is in the polling delay state. When the polling delay state is not reached or when the polling delay is completed, the polling is sent to the device A.

[Problems to be Solved by the Invention]

In the sequence of the conventional polling control method illustrated in FIG. 4, when the polling destination device becomes not ready and becomes ready immediately after it is retried out, polling Pol (A) is restarted. Device A cannot receive polling, so-called polling reception delay T1
If the polling is started from the not-ready state of each device at the time of system startup, there is a problem that the startup of the entire system is significantly delayed.

An object of the present invention is to minimize the polling reception delay at system startup.

[Means for Solving the Problems]

The present invention minimizes the polling reception delay by executing polling without polling delay when all the polling destination devices are in the not ready state at the time of system startup.

FIG. 1 is a principle diagram of the present invention and shows a control procedure of a polling sequence in a concrete example.

In the first polling sequence I, the polling device P
Polls the polling destination devices A and B.
Since there is no response together with (A) and Pol (B), it will be retried out after retrying.

In the next polling sequence II, it is recognized that all polling destination devices A and B have been retried out in the preceding polling sequence I, and the polling is executed without polling delay.

If the polling destination device A is in the ready state immediately before the polling Pol (A) is sent, Pol
Although the response (A) is returned to (A), the response to Pol (B) to the polling device B remains unresponsive.

In the subsequent polling sequence III, since there was a response from the polling destination device A in the previous polling sequence II, it was judged that the condition that all polling destination devices A and B were not ready was no longer satisfied, It returns to the same control method as the conventional polling control method. In this case, since there is no response from the polling destination device B, the polling is retried, resulting in a retry out and the polling delay T is set. After that, in consideration of the polling delay of the device B, the polling for the device B is thinned out until the polling delay T is completed, and when the polling delay T is completed, the polling for the device B is restarted.

[Action]

According to the present invention, when all of the polling destination devices are not ready and retry out in a certain polling sequence at the initial stage of system startup, the next polling sequence is immediately executed without polling delay.
The polling destination device that has changed to the ready state can immediately receive polling, and the polling reception delay is eliminated.

Further, in the subsequent normal operation state, the polling delay is performed for the polling destination device that has been retried out, so that the deterioration of the polling cycle for other devices capable of polling response is suppressed.

〔Example〕

 FIG. 2 is a configuration diagram of a system according to an embodiment of the present invention.

In FIG. 2, 1 is a polling source device P, 2, 3, 4 such as a host, and polling destination devices Sa, Sb, Sc, 5 such as terminals are transmission lines, and 6 is a polling sequence. A polling control device for executing a control procedure,
7, 8 and 9 are polling destination devices S-a and S-, respectively.
b, S-c, a polling slave device that controls polling.

Polling source device 1 (P) and polling destination device 2, 3,
4 (S-a, S-b, S-c) is performed via the transmission line 5 between the polling control device 6 and the slave devices 7, 8, and 9.

FIG. 3 is a flow of a polling control procedure of the polling control device 6 in the polling source device P. This flow shows a sequence procedure for cyclically polling each polling slave device 7, 8, 9 of the polling destination device S-a, S-b, S-c in that order. The number of connected subordinate devices in the system is represented by m, and the number of subordinate devices during polling delay is represented by n.

Upon starting the polling operation, the polling control device 6 of the polling source device P first executes a polling control procedure for the polling destination device S-a. Here, it is checked whether or not there is a polling delay factor, and if polling delay is not set, polling for Sa is sent. If the polling delay is being set, it is checked whether the polling delay has been completed. If not, it is checked whether m = n at the end of the preceding sequence. If polling transmission is omitted and m = n,
Polling is sent even though the polling delay is in progress. On the other hand, if the polling delay is completed, the device S
-Send poll to a.

Then, the procedure goes to the polling control procedure for the apparatus S-b, the same control as in the case of the apparatus 5a is performed, then the polling control procedure for the apparatus S-c is executed, and the polling control procedure for the apparatus S-a is executed. After returning, the same operation is repeated thereafter.

The polling destination device can apply the same polling control procedure regardless of the number of devices.

〔The invention's effect〕

According to the present invention, since the polling delay is not performed at the initial startup when all the polling destination devices are in the not-ready state, the polling cycle for each polling destination device is shortened and the startup time is shortened. You can

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a block diagram of a system of an embodiment of the present invention, FIG. 3 is a flow chart of a polling control procedure according to an embodiment of the present invention, and FIG. 4 is a conventional polling control. FIG. 5 is an explanatory view of an example of a polling sequence according to the method, and FIG. 5 is a polling control procedure of the conventional method. In FIG. 2, 1: Polling source device P 2, 3, 4: Polling destination device S-a, S-b, S-c 5: Transmission line 6: Polling control device 7, 8, 9: Polling slave device

Claims (1)

[Claims] 1. When a polling source device polls a plurality of polling destination devices in a predetermined order, if a polling delay factor such as no response retry to polling occurs in a certain polling destination device, it is constant. In the polling control method in which the polling delay is set and the polling for the device is thinned during the polling delay, the polling delay factor occurs in all of the above polling devices. Then, a polling control method characterized by performing polling by ignoring the polling delay.