Omron CS1D DUPLEX SYSTEM - 10-2009 Operation Manual page 165

Duplex Communications Units
Normal Operation
Operation for Errors
The secondary Communications
Unit communicates with nodes
with which the primary
Communications Unit cannot
communicate.
CS1D CPU Units for Duplex CPU Systems with a unit version of 1.1 or later or
a CS1D CPU Unit for Single CPU Systems with a unit version of 2.0 or later is
required to use Duplex Communication Units using primary/secondary com-
munications. CX-Programmer version 2 or higher is required for duplex set-
tings.
Up to three pairs of Communications Units using primary/secondary commu-
nications can be used for one CS1D PLC. The are also restrictions in the
number of Duplex Communications Units. Refer to the operation manuals for
the duplex Communications Units for details.
With duplex communications using primary/secondary communications,
memory is allocated for two unit numbers. Although the same unit number is
set for both Units, the primary Communications Unit uses the unit number that
is set and the secondary Communications Unit uses the next higher unit num-
ber. For example, if both Units are set to unit number 0, the memory normally
allocated for unit numbers 0 and 1 will be allocated to the duplex Communica-
tions Units. The unit number for these duplex Communications Unit cannot be
set to 15.
Using a number of pairs of duplex Communications Units using primary/sec-
ondary communications will restrict the number of other CPU Bus Units that
can be used, as shown in the following table.
Number of pairs of Communications
Units using primary/secondary
communications
0
1
2
3
The primary Communications Unit
communicates with other nodes
through the primary network.
Primary network
Secondary network
If the primary Communications
Unit fails, the secondary
Communications Unit performs
all communications.
16
14
12
10
Section 3-3
Allowable number of
other CPU Bus Units.
129