JPS63198437A - Polling system - Google Patents

Abstract

PURPOSE:To reduce the polling period by providing a polling address table and an address pointer to a host device so as to limit the reference of a terminal device state table for the required reference only. CONSTITUTION:An address pointer 21 has an stepping means 22 to address a polling address table 23. A flag representing the effectiveness of all address in the table 23 is set to logical 1 in the initial state to make the table 23 ineffective. The host device applies polling through a means 29 by using a timer control circuit 31 and a multiplexer 30 at each prescribed period regardless of the content of a state table 25 of the terminal device. As a result, if the terminal device is changed into the reply state, a revision pointer 26 and a multiplexer 28 register a terminal device address to the table 23. Then the pointer 26 is counted up by an stepping means 27 to bring the level of a registered bit to a level '1'.

Description

[Detailed Description of the Invention] [Summary] The present invention includes a polling address table for holding addresses when a small number of terminal devices are actually connected to a host device. , polling is performed according to the read terminal device address. This simplifies the severing procedure and significantly shortens the polling time.

[Industrial application field]

The present invention relates to an efficient polling method when the number of terminal devices is smaller than the number that can be connected to a host device.

[Conventional technology]

Conventionally, as shown in FIG. 4(G), a host device 1 is connected to a plurality of terminal devices 21 to 23, etc. via a bus 3 and a serial interface.

In order to detect the status of each of these terminal devices 21 to 2s, a method in which polling is performed from the host device 1 is often used.

FIG. 6 (6) is a configuration diagram of the main parts when polling is performed by the host device 1 of this system.

In the figure, a polling address register 11 is a register having an incrementing means 12, and holds the address of a terminal device to be polled, and uses this address to access a terminal device status table 13, and also provides a selection signal for the terminal device to be polled. . Terminal device status table 13
is accessed by the polling address register 11] and holds the latest status of the terminal device corresponding to each address. When accessing, this content is referenced and if the corresponding terminal device is not connected or powered on, control is passed.

FIG. 6 (6) is a flowchart showing the operation of the above configuration.

Set the 0th address of the terminal device status table 13 in the polling address register 11, read the corresponding status of the corresponding terminal device status table 15, check whether it is connected to the host device, and check whether it is connected to the host device. polling is performed, the polling address register 11 is incremented, and the next terminal device address is set.

If it is not connected, the polling address register 11 is incremented to advance to the next terminal device address as described above.

[Problem that the invention seeks to solve]

With the polling method described above, the unconnected
Even if there is a terminal device whose power is not turned on, polling is performed by sequentially referring to all the contents of the terminal device status table regardless of the presence of the terminal device. Therefore, if the number of devices that are actually connected to the host device is much smaller than the maximum number that can be connected to the host device, there will be many unnecessary references to the terminal device status table, and the polling cycle will be longer than the actually required polling cycle. A problem arose.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polling method that reduces the polling cycle by limiting reference to the terminal device status table to only what is necessary.

[Means for solving problems]

In order to achieve the above object, the present invention provides a polling address table for holding each address of a terminal device actually connected among a plurality of terminal devices connectable to a host device, and a polling address table for holding each address of a terminal device actually connected to a host device, and It is equipped with an address pointer for sequentially reading out each address.

[For production]

Polling Address Chee. Since only the addresses of terminal devices that are actually connected are registered in the pull, there is no need to refer to the status of terminal devices that are not connected, and polling can be performed at the shortest cycle.

That is, as shown in the principle explanatory diagram of FIG. 1, a flag is provided for each terminal device address 23-1 in the polling address table to indicate whether it is valid or invalid and processing is performed, thereby omitting the procedure of referring to the status.

〔Example〕

FIG. 2 is a configuration explanatory diagram of an embodiment of the main part of the present invention. In the same figure, an address pointer 21) 1 increment means 22
and addresses the polling address table 23. As shown in FIG. 1, each address 25-1 to 25-(n+1) of this polling address table 23 includes a terminal device address 23-1-2 and a 7-lag 23-1 to indicate the validity of the address. -1 is stored.

This flag is initially set to "1" and the polling address table 23 is all invalidated.

The host device uses the timer control circuit 31 and the multiplexer 30 to perform polling once every fixed period using means 29 not based on the present invention, regardless of the contents of the terminal device status table 25. As a result, the status of the terminal device If the registered bit in the terminal device status byte is "0" when the terminal changes from no response to response, the corresponding terminal device address is registered in the polling address table 23 by the update pointer 26 and the multiplexer 28. At that time, the flag 23-1-1 is reset to validate that byte. Thereafter, the update pointer 26 is incremented by the incrementing means 27, and the corresponding registered bit is further set to 11''.

The polling address table 230 is not updated when the status of the terminal device does not change or when there is another change (including a change from response to no response).

A flowchart showing how the polling address table 230 is updated is shown in FIG. 3 (α).

FIG. 3(b) is a flowchart showing the normal operation of the embodiment.

In the figure, the address pointer 21 is set to @0'', the polling address table 23 is read, the flag is checked to see if it is valid or invalid, and if the flag is valid, polling is performed and the polling address register 11 is incremented.If invalid, the polling address register 11 is incremented. Immediately increments the polling address register 11. Therefore, polling is performed only for valid polling target terminal devices.

〔Effect of the invention〕

As described above, according to the present invention, reading of the flag shown in FIG. 1 for unconnected terminal devices is completely omitted. Reading the flag is not a time issue as the address pointer is simply reading data, and efficient polling is performed which only involves the polling period for the connected terminal equipment.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of the configuration of an embodiment of the main part of the invention, Figs. 3 (α) and (6) are a flowchart showing the operation of the embodiment, and Fig. 4 (a), (6), (C)
is an explanatory diagram of a conventional example. In the diagram, 1 is a host device, 21 to
23 is a terminal device, 3 is a path, 21 is an address pointer,
22 is a stepping means, 23 is a poudang address table,
23-1.2. - indicates the terminal device address storage contents.

Claims (1)

[Scope of Claims] A data system in which a plurality of terminal devices are connected to a host device in a serial manner via a serial interface, and the host device polls the terminal device in order to detect the status of the terminal device. a polling address table for holding each address of a terminal device actually connected among a plurality of terminal devices connectable to the host device; and an address pointer for sequentially reading each address from the polling address table. A polling method characterized by: