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APPENDIX C — INPUT/OUTPUT BOARD (IOB) STATUS INDICATORS
All control boards have LED indicators that show control
board and communication status.
A red LED on each control module operates in the follow-
ing manner:
• Power not present or power supply failure: LED is off
• Power present but microprocessor in Reset: LED is off
• Microprocessor operational but not communicating:
LED flashes 3 seconds on, 3 seconds off
• Microprocessor operational and communicating with
control system: LED flashes at 0.5 Hz rate (1 second on,
1 second off) in sync (±100 ms) with all other new con-
trol modules on the same communication bus
• Microprocessor in boot mode: LED flashes at 0.2 sec-
onds on, 0.2 seconds off
Each independent communication port has a green status
LED. The green LED is on when data is being transmitted by
the board.
All RS485 ports have a green LED.