Chapter 18 Data Communications Between Target Device And Cpu Module In M:n Basis; Considerations On Data Communications - Mitsubishi Electric MELSEC iQ-R Series User Manual

18
DATA COMMUNICATIONS BETWEEN TARGET
DEVICE AND CPU MODULE IN M:N BASIS
Always read this chapter when communicating data by the multidrop connection in the system configuration
that the target device and CPU module are connected on an m:n basis.
This section explains data communications between the target devices and the CPU module by the multidrop connection of
multiple target devices (m stations) and C24s (n stations). (The total number of 'm' and 'n' is up to 32 stations.)
With this m:n multidrop communication, only MC protocol data communications by command transmission from the target
devices can be performed.
18.1

Considerations on Data Communications

Concurrent data communication with multiple target devices
When communicating data in m:n system configuration, more than one target devices cannot communicate data with the CPU
module at the same time.
Configure interlock among the target devices so that the target device can communicate data with the CPU module in a 1:1
basis.
For details on arrangement and method for interlock among target devices, refer to the following sections.
Page 368 Arrangement for Interlock among Target Devices
Page 371 Examples of Procedure for Data Communications with CPU Module
Data communication method
Data communication between target devices and the CPU module can be performed by the following methods only:
• Data communication with the full-duplex communication method (The m:n data communications is impossible with half-
duplex communications)
• Data communications by command transmission from target device using the MC protocol excluding the format 3 and
format 5 control procedure (Data communications using the format 3 and format 5 control procedure and data transmission
from sequence program using the on-demand function cannot be performed.)
Data transmitted from any of target devices
Data transmitted by one target device is received by all the other target devices, including the target device that transmitted
the data. The sent data from the CPU module is also received by all the target devices.
Therefore, devices that received data not addressed to their own stations (by judging by the station number in a message) are
required to ignore the received data.
At the CPU module side, C24 also ignores the received data not addressed to it.
18 DATA COMMUNICATIONS BETWEEN TARGET DEVICE AND CPU MODULE IN M:N BASIS
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18.1 Considerations on Data Communications