State Industries GFK-0827 manual RCM System Status Leds, Board OK

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			PRIMARY UNIT					SECONDARY UNIT			a47005
				( RACK 0 )					( RACK 0 )
P	C	B		R	G	P	C	B	R	G
S	P	T		C	B	S	P	T	C	B
	U	M		M	C		U	M	M	C
					31					30

Redundancy Communications Link

Redundancy Communications Link

Figure 6. Example of RCM Location in a Hot Standby CPU Redundancy System

RCM System Status LEDS

A Hot Standby CPU Redundancy system has two RCM modules, each with five LEDs and a momentary pushbutton switch for manually switching between the active and the backup units. The LEDs will always be updated by the appropriate system. The RCM has two internal timers that will automatically turn off four of the LEDs (not the board OK LED) if the LEDs have not been updated within a specified time period. The two remote LEDs and the two local LEDs have separate timers since they are controlled from different systems.

The RCM has five LEDS:

HBOARD OK

HLOCAL SYSTEM READY

HLOCAL SYSTEM ACTIVE

HREMOTE SYSTEM READY

HREMOTE SYSTEM ACTIVE.

These LEDs report the status of the health of the RCM and the control status of the Hot Standby CPU Redundancy system. The status provided by these LEDs is also provided in an area of %S memory (%S33 - %S39) which is accessible from the user logic program but cannot be altered or overridden. The LEDs have the following meanings and uses. Note that the term Local Unit when associated with a particular RCM refers to that unit in which the RCM resides. Remote Unit refers to that unit in which the RCM is configured by the system for addressing as being in rack 7, slot 1. Each RCM will have an associated local and remote unit.

BOARD OK

This LED will come on when the diagnostics are complete and the RCM has been determined to be operating normally. It will remain on unless the RCM fails.

LOCALSYSTEM READY

Indicates whether the local unit is ready to become the active unit in a redundant PLC configuration. If the LED is on, the local unit has been configured for redundancy, is in RUN mode, and has performed sufficient initialization, diagnostics, and hand±shaking to take control of the redundant system if selected as the active unit. It is the responsibility of the local unit to set the state of this LED at least once during each sweep; if the local unit is unable to set (or fails to set) the state of the LED, the hardware will force the LED to off after the timer has timed out.

20 Series 90-70 Hot Standby CPU Redundancy User's Guide ± December 1993 GFK-0827