7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL

MELSEC-Q

POINT

(1)The position and size of the transmission area in the buffer memory can be changed with GX Configurator-SC in accordance with the specifications of the external device and the transmission data length. (See Section 8.4.5.)

(a)When changing the position and size of the transmission area in the buffer memory with GX Configurator-SC, designate as follows:

1)Transmission buffer memory head address designation Designate the starting address for the area to be used as the transmission area in the user definable area of the buffer memory (address: 400H to 1AFFH, 2600H to 3FFFH).

2)Transmission buffer memory length designation

Designate by addresses the length of the area (0001H to 1A00H) to be used as the transmission area in the user definable area of the buffer memory (address: 400H to 1AFFH, 2600H to 3FFFH).

(b)If the following functions are also used when the position and size of the transmission area in the buffer memory are changed, make sure that the addresses of the transmission area do not overlap with those for the buffer memory that stores the transmission and receive data to be used by these functions.

1)MC protocol buffer memory read/write function

2)MC protocol on-demand function

3)Non procedure protocol transmission/receive function

4)Bidirectional protocol transmission/receive function

5)Communication data monitoring function

(2)Set the size of data per data transmission from the PLC CPU to the external device to be smaller than the size of the transmission data designation area in the buffer memory.

(Transmission data designation area) ≥ (Size of data portion to be sent from the PLC CPU)

To transmit data whose size is larger than the transmission data designation area, increase the transmission area, or divide the transmission data before sending.

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