6 DATA COMMUNICATION USING THE NON PROCEDURE PROTOCOL MELSEC-Q

6.1.4 Receive data clear

For the data reception by a non procedure protocol, if the transmission of data from a transmitting device is interrupted due to trouble occurring, it may be necessary for the data received up to the present time are cleared in the receiving device and for the data to be received again from the start.

The methods for clearing reception data in the Q Series C24 is shown below. Either method may be used to clear the reception data as is necessary.

1)Clear the reception data by the dedicated instruction "CSET."

2)Write to/read from the reception data clear request area (address A8H/148H). (FROM/TO instruction)

3)Clear the reception data by GX Configurator-SC (see Section 8.7).

REMARK

When transmitting data to an external device from the Q Series C24, do not execute a clear request of the reception data shown in this section.

If a reception data clear request is executed when transmitting data to an external device, The Q Series C24 stops data transmission and terminates the dedicated instruction for transmission abnormally. (The transmission completed signal does not go ON.) If a reception data clear request is executed during data reception, the data received up to that point are cleared.

(1) Receive data clear processing

The Q series C24 performs the following procession when the receive data clear is performed.

•The data received up to that point can be ignored.

•The receive data count up to that point is "0".

(The receive area in the buffer memory is not initialized).

• Set to the status prior to the start of data reception.

(2)Procedure for clearing the reception data by the dedicated instruction "CSET"

This instruction clears the reception data up to the present without interrupting the data transmission processing.

(Procedure for clearing) ··· In case of the CH1 side interface

1)Execute the CSET instruction

If the CSET instruction is executed while the read request (X03/X0A) or reception abnormal detection signal (X04/X0B) is turned on, the CSET instruction is kept waiting until the signal is turned off.

2)The reception data clear processing is executed at the OS area of the Q series C24 (see Section 6.1.2).

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