Redundancy System Requirements

For a redundant CPU configuration using the Hot-Standby Redundancy scheme to be valid, the following requirements must be true in both the Primary Unit and the Secondary Unit in the redundancy system.

HOne configuration must be set to Primary; the other to Secondary.

HThe control strategy configurable parameter must be set to ºGHSº.

HAn RCM must be configured in rack 0 of each system. There can be no empty slots between the RCM and the CPU. For a given unit, the Local RCM is the one configured in that unit; the Remote RCM is not configured by the user, but is automatically configured by the system to be in slot 1 of rack 7.

HAll Genius Bus Controllers in the system must be configured for RED CTRL Redundancy with the redundant pair set for EXTERNAL, or they must be configured for no redundancy.

HIf a Genius Bus Controller is set to redundant in a redundant CPU configuration, all of its bus blocks must also be set redundant; if a Genius Bus Controller is set non-redundant in a redundant CPU configuration, all of its bus blocks must also be set non-redundant.

HIf the primary/secondary configurable item is set to PRIMARY, all Genius Bus Controllers configured for RED CTRL redundancy must have Serial Bus Address 31. If the primary/secondary configurable item is set to SECONDARY, all Genius Bus Controllers configured for RED CTRL redundancy must have Serial Bus Address 30.

HThe Shared I/O selections must match exactly between Primary and Secondary PLCs.

Basic Redundancy System Setup

HAssemble each PLC system and cable the last rack of each system to the RCM of the other PLC using the terminated I/O cable. If there are no expansion racks in the system, cable each BTM to the RCM in the other PLC.

Logicmaster 90 Configuration

HSet the primary CPU to PRIMARY.

HSet the secondary CPU to SECNDARY.

Forboth Primary and Secondary CPUs, do the Following:

HSelect Data Transfer (SHARED I/O) parameters (up to 20 Kbytes Input data, up to 28 Kbytes Output data).

HConfigure the SBA for all Redundancy Genius Bus Controllers (SBA 31 for the Primary; SBA 30 for the Secondary), and Redund Mode to ºRED CTRLº.

HSelect fail-wait time. The default value of 60 ms should suffice for most applications.

HSelect watchdog timer. Allow for worst case scan time plus data transfer time plus two fail-wait times (plus a generous margin). Setting this value too small could cause the standby unit to time out during a failure of the active unit.

HSelect the programmer window. Set to about 10% of the normal scan time (if scan time is unknown, use default time (do not exceed the fail wait time).

HSelect Fault Actions.

I/O System Configuration

HConfigure your I/O system as required for your application.

Series 90-70 Hot Standby CPU Redundancy User's Guide ± December 1993

State Industries GFK-0827 manual Redundancy System Requirements, Basic Redundancy System Setup

Models: GFK-0827