Mitsubishi Electric MELSEC iQ-RJ71C24-R2 - Data Communications between Target Devices and CPU Module by Designating a Master Station and Slave Stations

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18 DATA COMMUNICATIONS BETWEEN TARGET DEVICE AND CPU MODULE IN M:N BASIS
18.3 Examples of Procedure for Data Communications with CPU Module
Data communications between target devices and CPU module
by designating a master station and slave stations
One of the target devices becomes the master station and the other target devices communicate data with the CPU module
after obtaining permission from the master station.
Ex.
The example below shows the procedures for each target device to communicate data with the CPU module.
In this example, after the start of data communications between a target device and the CPU module, each device checks for
timeout of the maximum data communication time. In addition, devices on the slave station, which are not communicating
data with the CPU module, check if the target device that completed data communications with the CPU module transmitted a
communication complete report.
In the following descriptions, the target device with the lowest station number(1BH) is the master station and the other target
devices are slave stations.
Ex.
 A slave station that wants to communicate data with the CPU module sends a communications request to the master
station to obtain the line ownership. A message structure example is shown in .
Time
Master station
target device
Permission
granted
response
General report to
start and end data
communications
between master
station and
CPU module
Communications
request
Communications
complete report
Communications
request
Communications
complete report
Slave station
target device 1
Communications
request
Response
Permission
granted
response
Respo
nse
Permission
granted
response
Slave station
target device 2
End
Start
Slave station
target device m-1
Data
communications
with CPU module
Data
communications
with CPU module
Data
communications
with CPU module
ÓÒ
CPU CPU CPU
C24 C24 C24 C24
CPU
(Before Ó)
(after Ó)
Master station
Target device Target device Target device Target device
(Station No.:1BH) (Station No.:1CH) (Station No.:1DH) (Station No.:1EH)
(Station No.:0H)
(Station No.:15H)
(Station No.:2H)
(Station No.:1H)
Target device that obtained the line ownership
The above C24 includes Q series C24, L series C24, QC24(N), and UC24.