5
FUNCTIONS
5.2 Master Function
5.2.1 Automatic communication function
5 - 12
1
OVERVIEW
2
SYSTEM 
CONFIGURATION
3
SPECIFICATIONS
4
MODBUS(R) STANDARD 
FUNCTIONS
5
FUNCTION
6
PRE-OPERATIONAL 
PROCEDURES AND 
SETTINGS
7
PARAMETER SETTING
8
UTILITY PACKAGE 
(GX Configurator-MB)
(5) Start and stop of the automatic communication function
(a) When the automatic communication parameters are set on GX Configurator-MB
When the automatic communication parameters are set on GX Configurator-MB, 
no sequence program for start is required.
1) Operation timing of the automatic communication function
The automatic communication function is activated by powering ON the 
programmable controller from OFF or by resetting the programmable 
controller CPU (with the programmable controller CPU's RUN/STOP switch 
set to RUN). 
The automatic communication will not start if the programmable controller is 
powered ON from OFF or if the programmable controller CPU is reset (with 
the programmable controller CPU's RUN/STOP switch set to STOP). 
If the QJ71MB91 is mounted on a MELSECNET/H remote I/O station, the 
automatic communication function is activated when the remote I/O station 
receives the information notifying the status change (from STOP to RUN) of 
the remote master station's programmable controller CPU.
2) How to check the activation of the automatic communication function
When the QJ71MB91 starts communication with the slave device with the 
automatic communication function, the SD and RD LEDs turn ON. (Only when 
communicating)
3) Automatic communication start/stop test
On the "Automatic communication status" screen of GX Configurator-MB, the 
start/stop test of the automatic communication function can be performed. 
(  Section 8.6.3)