7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL

MELSEC-Q

(Program example)

When Q series C24 I/O signals are from X/Y00 to X/Y1F:

 

 

 

 

 

 

 

 

 

Designate the receive channel.

 

 

 

 

 

 

 

 

 

Clear the receive data count storage device

 

 

 

 

 

 

 

 

 

to 0.

 

 

 

 

 

 

 

 

 

Designate the allowable receive data count.

 

 

 

 

 

 

 

 

 

With the normal completion, the receive

 

 

 

 

 

 

 

 

 

data within the allowable receive data count

 

 

 

 

 

 

 

 

 

(user designated) is read from the receive

 

 

 

 

 

 

 

 

 

data storage area in the buffer memory.

 

 

 

 

 

 

 

 

 

• After the BIDIN instruction is executed,

 

 

 

 

 

 

 

 

 

the user designated read completion

 

 

 

 

 

 

 

 

 

signal (M0) comes on for 1 scan.

 

 

 

 

 

 

 

 

 

• The reading of received data is performed

 

 

 

 

 

 

 

 

 

by the PLC CPU.

 

 

 

 

 

 

 

 

 

Q series C24

 

 

 

 

 

 

 

Address

 

Buffer memory

 

 

 

 

 

 

 

 

 

For normal completion

 

 

 

 

 

258H

 

Data reception result storage area

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D 0

 

 

 

 

 

 

 

 

 

 

 

Interface number

(1)

 

 

 

 

600H

 

 

 

 

 

 

 

 

 

 

 

 

Receive data count storage area

 

D 1

Reception result

(0)

 

 

 

 

 

 

 

601H

 

 

 

 

D 2

Receive data count

(n)

 

 

 

 

 

 

 

 

 

 

 

 

 

D 3

Allowable receive data count

(10)

 

 

 

 

to

 

Receive data storage area

 

 

 

 

 

 

 

7FFH

 

 

 

 

 

 

 

 

 

 

 

 

D10 Receive data

 

 

 

 

 

 

 

 

 

 

 

 

 

 

to

to

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D m

Receive data

 

 

 

 

 

 

 

 

 

 

When the received data count is larger than the allowable received data count, only the data up to the allowable received data count will be stored and the excess data will be discarded.

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