Master Function; Automatic Communication Function - Mitsubishi Electric QJ71MB91 User Manual

5
FUNCTIONS

5.2 Master Function

This section explains the functions of the QJ71MB91 acting as a MODBUS master.

5.2.1 Automatic communication function

The automatic communication function is a function by which device read/write request
messages are automatically issued from the QJ71MB91 to the MODBUS compatible slave
devices.
Device memory
Programmable controller CPU
Device memory
Auto Refresh
5
- 3 5.2 Master Function
5.2.1 Automatic communication function
QJ71MB91 (Master function)
Buffer memory
Read
Read
Read
Write
Automatically issues the
MODBUS device read/write
request message to Slave.
Figure 5.1 Communication using the automatic communication function
RS-485
Holding register
Holding register
Holding register
MODBUS slave device
(Third party remote I/O, etc)
MODBUS slave device
(Third party sensor, etc)
MODBUS slave device
(Third party programmable
controller)