User`s manual

334
CHAPTER 14 DATA COMMUNICATIONS USING
EXTERNAL DEVICE AND
PROGRAMMABLE CONTROLLER
CPU M : N CONFIGURATION
Always read this chapter when communicating data by using a multidrop link to connect the external devices and
programmable controller CPU in an m: n system configuration. You do not have to read this chapter when using a system
configuration other than
m: n to communicate data.
This section describes the case when data is communicated between external devices and the programmable
controller CPU by connecting multiple external devices (m stations) and multiple Q series C24 (n stations) over a
multidrop link. (The total number of m and n is up to 32 stations.)
With this m : n multidrop link, only MC protocol data communications by command transmission from the external
devices can be performed.
14.1 Data Communications Precautions
(1) When communicating data by using an m: n system configuration, multiple
external devices cannot communicate data with the programmable controller
CPU at the same time.
Interlock the external devices so that the external device can communicate with the programmable controller
CPU in a 1:1 configuration.
See Page 336, Section 14.2 to Page 339, Section 14.3 for the items to be agreed upon and the interlock method
to interlock the external devices.
(2) Communicate data between external devices and the programmable controller
CPU by the following methods only.
• Full-duplex data communications (m : n data communications is impossible with half-duplex data
communications)
• Data communications by command transmission from external device using an MC protocol excluding the
format 3 and format 5 control procedure (Data communications using the format 3 and format 5 control
program and data transmission from sequence program using the on-demand function cannot be
performed.)