Local and Distributed I/O Restrictions

Overview

A Quantum Hot Standby has the following I/O restrictions:

In an Quantum Hot Standby system both Local I/O and Distributed I/O (DIO) can be used, they are not part of the redundant system.
Local output can be dedicated to and managed by each PLC in their local racks.
When local or Distributed I/O are used, they have to be managed in the first section of the MAST task of the application by using located %MW that are not transferred from the Primary CPU to the Standby CPU.
Distributed I/O are not compatible with the safety processor (140 CPU 671 60S).

WARNING

RISK OF EQUIPMENT DAMAGE

MB+ DIO: output values must be evaluated only if a primary and a standby CPU are running. If at least one CPU is offline then outputs have to be managed in fallback.

Failure to follow these instructions can result in death, serious injury, or equipment damage.

Local I/O Management

It is possible to manage outputs locally in both PLCs. They may be written with different values at the same time that depends on application program processing. For that, the first section of the MAST task of the application must be used. On the other hand, only the located variables that are not transferred from the Primary to the Standby must be used for managing the different values applied on the output modules.

When outputs are managed locally in each PLC, the output values must be evaluated in the first section of the MAST task at each PLC scan. If this is not done, the Standby output value is erased by the value coming from the Primary PLC.

NOTICE

RISK OF EQUIPMENT DAMAGE

Output values must be evaluated in the first section of the MAST task at each scan.

Failure to follow these instructions can result in equipment damage.

Handling I/O

The Quantum Hot Standby system supports I/O connected to a RIO drops and DIO connected using I/O scanning.

NOTE: DIO devices can be scanned by one or more 140 NOC 78• 00 DIO modules.

Local I/O can be configured and run, but is not redundant in a Quantum Hot Standby system.

Local I/O and PLC Modes

Local I/O is treated differently according to the operating mode of its PLC:

Primary RUN

The Local I/Os are updated by the application running in the Primary CPU and is exchanged with Standby CPU.
Standby RUN

The Local I/Os are updated by the application running in the Standby CPU.
Run OFFLINE
- All sections of the MAST task are executed
- Only the first section of the MAST task is executed
- No sections of the MAST task are executed

NOTE: The system updates the Local I/O in Run OFFLINE.

NOTE: No data are transferred from the primary CPU to the OFFLINE CPU.