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Checking Operations of CS-series and CJ-series Master Units
Section 6-3
Input Slave Communications Error Flags
These flags indicate whether a communications error has occurred with the
corresponding Input Slaves.
Note 1. Input from Input Slaves and output to Output Slaves is enabled when the
CompoBus/S System is started up and the Active Node Flag correspond-
ing to the Slave is turned ON. During actual operation, it is recommended
to create a ladder program that processes Slave I/O after checking that Ac-
tive Node Flags are turned ON and Communications Error Flags are OFF.
2. When a CS-series or CJ-series Master Unit is set to communications stop
mode, communications will stop when the Output Slave Communications
Error Flag or Input Slave Communications Error Flag turns ON.
6-3-3 Checking Status Using Special I/O Unit DM Area
A CS-series and CJ-series Master Unit is allocated an area in the PLC's Spe-
cial I/O Unit DM Area for setting and information storage for the Slave registra-
tion function and communications stop mode. Use a Programming Device
(such as the CX-Programmer) to read the area and check the communica-
tions status and which Slave the error occurred in.
Master Unit’s DM Area
Words and Configuration
The following table shows the location and configuration of the Special I/O
Unit DM Area words used by a CS-series and CJ-series Master Unit.
Flag status Meaning
0 (OFF) Normal communications or the Slave is not participating in communi-
cations.
1 (ON) Withdrawn from communications (communications error)
(This flag turns OFF automatically when the Slave rejoins communi-
cations.)
PLC Location of Status Area
CS-series and CJ-
series PLCs
First word = D20000 + unit number × 100
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