Troubleshooting Primary PLC

Overview

To determine which component has become inoperative note the:

controller status displayed in the CPU LCD screen
RIO Head status displayed in the RIO Head LEDs

Troubleshooting the Primary CPU

This table gives the location of Primary PLC detected errors:

Controller Status	RIO Head Status	Detected Error Type	Description
Stop	All LEDs off except Ready on and Com Act blinks four times	Controller	A detected interface error occurred.
Offline	All LEDs off except Ready on	Fiber Optic connection between PLCs	A communication error was detected.
Stop	All LEDs off except Ready on and Com Act displays a detected error pattern	RIO Head	A communication error was detected.
Stop	Ready on and Com Act blinks four times	RIO Cable becomes inoperative at Primary CPU End	In a dual cable system, if only one cable is inoperative, the Error A or Error B LED on the RIO Head lights up instead of stopping the system. NOTE: When the RIO cable becomes inoperative at the Primary CPU end, the input data may be reset to 0 for one scan because the communication interruption to the drop occurs before the broken link is detected.

NOTE: In a Quantum Hot Standby configuration without RIO drop, the A and B detected error LEDs are not relevant when using CRP module with a firmware version lower than 2.00.

Troubleshooting the Standby CPU

This table gives the location of Standby PLC detected errors:

Controller Status	RIO Head Status	Detected Error Type	Description
Stop	All LEDS off except Ready on or Ready on and Com Act blinks once a second	Controller	A detected Interface error occurred.
Offline	Ready on and Com Act stops blinking	Fiber Optic connection between both controllers	A detected communication error occurred.
Stop	Com Act displays detected error pattern	RIO Head	After replacing the module and cycled power, to ensure that the controllers have identical application programs, perform an application program update.
Stop	Ready on and Com Act blinks four times	RIO Cable becomes inoperative at Standby CPU end	In a dual cable system, the RIO Head gives no indication if only one cable has become inoperative.
Offline	Com Act on	Either type of fiber link interruption: from Standby CPU Transmit to Primary CPU Receive from Primary CPU Transmit to Standby CPU Receive