Troubleshooting Primary PLC
Original instructions
Overview
To determine which component has become inoperative note the:
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