Schneider Electric 840 USE 106 0 CHS Instruction, Execute Hsby Unconditionally Enable Command

Using a Quantum 984 HSBY System

CHS Instruction

Using CHS

Instruction

Using the CHS Instruction to Control Your Hot Standby System

CAUTION

Reschedule Segment Hazard

To help protect against damage to application I/O devices through unexpected system actions, do not reschedule segment 1 via the segment scheduler.

Failure to follow this precaution can result in injury or equipment damage.

Segment 1 may contain the ladder logic for diagnostics and optional Hot Standby functions, such as time-of-day clock updates.

If you choose to use the CHS instruction in ladder logic to control the Hot Standby configuration, the instruction must be placed in network 1, segment 1 of the ladder logic program. The top node must be connected directly to the power rail by a horizontal short. No control logic, such as contacts, should be placed between the rail and the input to the top node. However, other logic may be placed in network 1. Remember, the ladder logic in the Primary and Standby controllers must be identical.

The three nodes in the CHS instruction define the command register, the first register in the nontransfer area, and the length of the nontransfer area.

Execute HSBY

Unconditionally

Enable Command

Register

Enable Nontransfer Area

command register

nontransfer area

CHS

length

HSBY System ACTIVE

PLC cannot communicate with its CHS module

Configuration extension screens are defining the HSBY configuration

The bottom output node of the CHS instruction indicates whether the configuration extension screens have been activated and allows the parameters in the screens to override those in the CHS instruction at startup.

A detailed description of the CHS instruction is provided in the Ladder Logic Block Library User Guide.

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