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5.3 Slave Function
5.3.1 Automatic response function
5
FUNCTIONS
5.3 Slave Function
This section explains the functions of the QJ71MB91 acting as a MODBUS slave.
5.3.1 Automatic response function
By the automatic response function, the QJ71MB91 (slave function) automatically
executes the processing requested by the function code (
Section 4.1) of a request
message from the master, and returns a response message to the master.
For device read/write or exception status read, use the MODBUS device assignment
function. (
Figure 5.12 Automatic response function
Programmable
controller CPU
QJ71MB91
(Slave function)
1)
2)
3)
4)
No sequence
program
required
Device memory
Receiving
request message
Function
code
identification
Requested
processing execution
Transmitting
response message
Request message (function code)
Response message
RS-232, RS-422 or RS-485
R
MODBUS
master device
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