Mitsubishi QJ71MB91 User Manual

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5.3 Slave Function
5.3.3 Link operation function
5
FUNCTIONS
5.3.3 Link operation function
(1) The link operation function
The link operation function enables the master connected to CH1 (RS-232) to
communicate with multiple slaves connected to QJ71MB91's CH2 (RS-422/485).
If the link operation function is used, a RS-232 interface (1-to-1 communication)
MODBUS master device can communicate with several MODBUS slave devices.
(2) Setting the link operation function
The link operation function can be set with the intelligent function module switch
( Section 6.6).
(3) Message flow during link operation
A request message received on CH1 is sent to a slave from CH2.
A response message received from CH2 is sent to the master from CH2.
If a request message addressed to the QJ71MB91 is received, the QJ71MB91 will act
as a slave. (The link operation is not performed.)
Figure 5.16 Communication using the link operation function
Figure 5.17 Message flow during link operation
4
2
5
3
1
6
7
(FG)
(FG)
RS-232
/485
RS-422
CH2
RDB
RDA
SDB
SG
SDA
CH1
QJ71MB91
RUN
RD
NEU.
SD
NEU.
RD
SD
CH1
CH2
ERR.
R
R
R
MODBUS master device
QJ71MB91 (Slave function)
CH1(RS-232)
CH2 (RS-422 or RS-485)
MODBUS
slave device
MODBUS
slave device
Request
message
Response
message
R
R
R
Operates as a slave
when receiving request
message addressed to
QJ71MB91
MODBUS
master device
Programmable
controller CPU
CH1:
RS-232
Messages are relayed
from CH1 to CH2
or from CH2 to CH1.
CH2:
RS-422
/485
QJ71MB91
(Slave function)
MODBUS
slave device
MODBUS
slave device
Request
message
Response
message

Mitsubishi QJ71MB91 Specifications

General

Brand	Mitsubishi
Model	QJ71MB91
Category	Controller
Language	English