Primary And Secondary Communications - Omron SYSMAC CS1D-PD Series Operation Manual

Duplex Communications Units
Normal
communications
3-3-2

Primary and Secondary Communications

Two Communications Units are connected to the same communications line.
One of them operates in Active Mode, the other one in Standby Mode. The
same unit number and node address are set for both of the Units.
The active (ACT) Communications Unit performs communications with the
nodes on the network. The standby (STB) Communications Unit runs on
standby while performing self-diagnosis. If the active Communications Unit
fails, the standby Communications Unit switches to Active Mode and contin-
ues communications operations.
Standby while performing self-
diagnosis. (Line performs node
bypass.)
ACT STB
CPU
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Active/standby communications have been supported since the first CS1D
CPU Units were released, so they can be used on any CS1D CPU Unit
(including Pre-Ver. 1.1 CPU Units). CX-Programmer version 3.1 or higher is
required to make settings for duplex operation.
Up to three pairs of Communications Units using active/standby communica-
tions can be used for one CS1D PLC. Even when using Duplex Communica-
tions Units, only one unit number is allocated and no restrictions apply to
using other CPU Bus Units.
Primary/secondary communications are used with CS1D Ethernet Units
(CS1D-ETN21D). Two Communications Units are connected, but each is con-
nected to a different communications line (network). One Unit operates as the
primary Communications Unit, the other as the secondary Communications
Unit.
The same unit number and node address are set for both of the Units, but two
unit numbers (twice the amount of memory) are allocated.
The primary Communications Unit performs communications with the nodes
on the primary network while confirming node participation in the primary net-
work. The secondary Communications Unit runs on standby while confirming
node participation in the secondary network.
If there is a broken line in the primary network and communications are not
possible for a specific node or nodes, the secondary Communications Unit will
take over and continue communications with those nodes. If the primary Com-
munications Unit fails, the secondary Communications Unit will take over all
communications previously performed by the primary Communications Unit.
Receives instructions from
CPU Unit and performs
normal operation.
Unit
error
CPU
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Section 3-3
137