Mitsubishi Electric QJ71MT91 User Manual

4 - 17 4 - 17
MELSEC-Q
4 MODBUS STANDARD FUNCTIONS
4.3.10 Write file record (FC: 21) (SC: 06)
Writes values to one or more extended file registers.
Number of accessible devices with one message
1 to 122 points
(1) Request message format (Master
→
Slave)
1: The upper limit of the file number available for the QJ71MT91 slave function
is equal to the file register size of the mounted programmable controller
CPU. (Refer to Section 7.4.4.)
2: N indicates the total number of write points (n1 + + nm).
(a) Specify the total write points of all the sub-requests, N (n1 + + nm)
so that the size of the PDU (protocol data unit) in the request message does
not exceed 253 bytes.
2 + m × 7 + N × 2 ≤ 253
If the above condition is not satisfied, the request message is discarded.

Mitsubishi Electric QJ71MT91 Specifications

General

Brand	Mitsubishi Electric
Model	QJ71MT91
Category	Control Unit
Language	English