Mitsubishi-electric QJ71C24N Manuel d'utilisateur télécharger pdf (Page 178)

7 - 27 7 - 27

MELSEC-Q

7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL

7.4 Data Communications Precautions

The following shows the precautions when performing data communications using the

bidirectional protocol.

(1) When the transmission sequence is in the initial status, it indicates that data

transmission and reception processing has not been started.

The Q series C24 transmission sequence is initialized in the following cases.

• The power is turned on, the CPU is reset.

• When operating, or the mode is switched.

• When a response message (ACK, NAK, etc.) was received in reply to data

transmission.

• When a response message (ACK, NAK, etc.) was transmitted in reply to data

reception.

• When the CD signal was turned off during data communications using Check

CD terminal in full-duplex communications through the RS-232 interface.

(2) As a data transmission procedure, data transmission from the external device or

the Q series C24 should be performed after an response for the immediately

preceding data transmission has been received.

(3) The external device and PLC CPU must agree so that the units of the data length

(word count/byte count) in the message to be transmitted and received is the same.

The PLC CPU units can be set using the GX Configurator-SC word/byte units

designation.

Make the length of the data area in the message to be transmitted and received

the size of the Q series C24 buffer memory transmission data designation area

and receive data storage area, or less.

(4) NAK code response

1) Response from the Q series C24 to external device

After the error detection message reception complete, it transmits the NAK

code to the external device.

2) Response from external device to the Q series C24

Transmit the error code (0022

to 005F

) immediately after the NAK

response.

1 2 ... 173 174 175 176 177 178 179 180 181 182 183 ... 357 358

Pas de commentaire

Mitsubishi-electric QJ71C24N Manuel d'utilisateur Page 178