Omron CS1D DUPLEX SYSTEM - 10-2009 Operation Manual page 117

Programming Devices
Leaving a PT or Host Computer Connected Constantly to RS-232C Port
Note
If a PT (Programmable Terminal) or host computer (running SCADA software)
is left connected constantly for monitoring a Duplex CPU System, and if the
connection is only to the active CPU Unit, then writing will become impossible
when an operation switching error occurs and the active CPU Unit becomes
the standby CPU Unit.
For that reason, it is recommended that the following connection be used. For
this, it is required that the Standby CPU Unit RS-232C Port Setting in the PLC
Setup be set so that independent communications are disabled (i.e., the
default setting).
PT Connection Example
In this example, communications between the CPU Unit and the PT are con-
tinued even after an operation switching error occurs.
Active CPU Unit
Standby CPU Unit
C S D P L01 C S C S
R U N D P L S T A T U S R U N
ER R /A LM A C T I V E ER R /A LM
R
C P U S T A T U S
I N H B K U P I N H B K U P
A C T I V E
L
P R P H C O M M C P U S T A T U S P R P H C O M M
R I G H T C P U
N O U SE
LEFT C P U
U SE
N O U SE
M O D E
O N O FF
SP L D P L
A C T. A C T.
LEFT R I G H T
O N
I N I T .
S W
C O M M
P R P H L
A 39512
R SV
O N
RS-422A/485 (See note a.)
Note a) Use shielded twisted-pair cable for the RS422A/RS-485 cable.
Model
CO-HC-ESV-3P 7/0.2
b) The CJ1W-CIF11 does not provide isolation. The total length of
the transmission path must therefore be 50 m or less. If the trans-
mission distance is greater than 50 m, use the NT-AL001, which
provides isolation, and do not include the CJ1W-CIF11 in the
transmission path. When only the NT-AL001 is used, the total
length of the transmission path can be a maximum of 500 m.
1. The above Conversion Adapter is not required for the RS-422A/RS-485
port at the PT.
2. When the CPU Units are switched, communications may be momentarily
interrupted, so enable communications retries in the PT communications
settings.
CJ1W-CIF11 R422A
Conversion Adapter or
NT-AL001 Link Adapter
(See note b.)
RS-422A/485 (See note a.)
Manufacturer
Hirakawa Hewtech Corp.
Section 2-6
PT
NS-AL002 RS-232C/RS-422A
Conversion Adapter for NS
Series
81