6 DATA COMMUNICATION USING THE NON PROCEDURE PROTOCOL MELSEC-Q

The following is a program example of clearing the reception data by the dedicated instruction "CSET."

Set the execution type

Set the request type (Reception data clear)

Execute the reception data clear

Normal completion

Abnomal completion

Reset the complete flag by external command

(3) Receive data clear procedure using FROM/TO instruction

Write and read the buffer memory receive data clear request area (addresses A8 H/148H) using the procedure described below.

When resuming data communications with an external device, resume it after completing the reception data clear processing with the Q Series C24.

Depending on the data communications system, it may be necessary to restart data communications with the external device after notifying the external device from the PLC CPU that resumption of communications is possible.

(Clear Procedure)· ··When the CH1 side interface is used.

(1)Since receive processing, send processing and receive data clear processing are not being performed, “1” is written to buffer memory address A8H using the TO instruction for the sequence program.

(2)Receive data clear processing is performed for the Q Series C24’s OS area (See Section 6.1.2).

(3)When receive data clear processing is completed, the value in buffer memory address A8H becomes “0.”

The following page shows an example of a program to clear receive data with the FROM/TO instruction.

Create a program that contains the contacts (user flags, etc.) indicating the following statuses in the TO instruction.

•Contact when the CHn reception data read request signal (X3/XA) is OFF

•Contact when the CHn reception abnormal detection signal (X4/XB) is OFF

•Contact indicating that send and receive processes are not currently being performed

•Contact indicating that reception data clear processing is not currently being performed

1 When the function version A Q Series C24 is used, resume data communications a further 100 ms after the buffer memory address A8H/148H value changes from a “1” to a “0.”

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