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Chapter 6
Error indication and Countermeasure
6.5
Error detection and running of CPU
In the case of compact remote system, remote modules continue communication when reverse double-transmission
error or time-out error occurs. These errors are not informed to CPU, so CPU continues running normally.
The communication error indication (CERR) is automatically turned off, if the communication returns normally.
And remote operation is continued.
Because transmission line consists of multi-drop system as shown in Figure 6.2, even if the breakdown of slave
module occurs, the remote operation between master and the other normal slave module continues and doesn't
become a system down. When the power supply in slave station is turned off, it is similar.
Master module
(EH-TRMME)
Normal
Figure 6.2 Fallback operation when breakdown in slave module occurs
However when the inconvenience is caused in breakdown of slave, cable disconnection, and power supply OFF in
slave, please take the following means to detect these abnormalities.
■ Slave abnormal detection method –1: the case unnecessary of HOLD function
When the HOLD function at communication fault (CERR) is unnecessary, please wire one point input in slave
station to always become turning on as shown in Figure 6.3. The ladder program observes this, and normality is
detected.
Program example detecting both of salve normality
X10000
Slave St.No.0
normal
Figure 6.3 Slave abnormal detection method –1 (the case unnecessary of HOLD function)
Breakdown
Master module
(EH-TRMME)
X
16
X11000
Slave St.No.1
normal
Slave module
(EH-TRMLE)
X
X
Y
16
16
16
Slave St.No.0
(EH-TRMLE)
X
Y
16
16
X10000 always ON
M200
Both of slave
normal
6 – 4
Slave module
(EH-TRMLE)
Y
Y
X
X
16
16
16
16
Normal
Slave St.No.1
(EH-TRMLE)
X
Y
X
X
Y
16
16
16
16
16
X11000 always ON
Y
16
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