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Publication 1785-UM012D-EN-P - July 2005

Troubleshooting F-9

Extended-Local I/O System

Troubleshooting Guide for the 1771-ALX Adapter Module

ACTIVE

ADAPTER

FAULT

I/O RACK

FAULT

Indicators Description Probable Cause Recommended Action

Active Adapter

Fault

I/O

Rack

On Off Off Normal indication;

remote adapter is fully

operational

Off On Off

Local adapter fault

(1)

Local adapter not operating; it will

stay in fault mode until fault is

corrected

Cycle power to the chassis to clear the

adapter fault.

(2)

Replace adapter if fault

does not clear.

Off Off On

I/O chassis fault

Problem exists between:

• adapter and module in chassis; the

module will stay in fault mode until

fault is corrected

• shorted printed circuit board runs on

backplane or I/O module

Cycle power to the chassis to clear a

problem resulting from high noise.

• remove and replace all I/O modules one at a

time

• replace adapter

• If problem does not clear, something is

wrong in chassis or I/O module

Blinking Off Off Outputs are reset Controller is in program or test mode

Local I/O Scanner is holding adapter

module in fault mode

None

Fault should be cleared by extended-local

I/O scanner.

Blinking alternately Off Adapter module not

actively controlling I/O

Adapter module in

controller restart lockout

mode (adapter to

scanner link is normal)

Controller restart lockout switch on

chassis backplane switch assembly

(3)

Press chassis reset button to clear lockout

feature or cycle power; if after repeated

attempts indicators are still blinking, check

that adapter module was reset by

controller/scanner, then immediately

faulted.

Off Off Off No power or no

communication.

Power supply fault Check power supply, I/O cable and power

supply cable connections, and make sure

adapter module is fully seated in chassis.

On Blinking Off Module placement error

in extended-local I/O

chassis

Incorrect placement of high-density

modules

Verify addressing modes and switch

settings.

(1)

Cycling power clears the block-transfer request queue. All pending block transfers are lost. Your program must repeat the request for block transfers from the chassis.

(2)

If a fault occurs and the controller is in the run mode but is actually operating in the dependent mode, the chassis fault response mode is selected by switch 1 (the last state

switch) on the chassis backplane.

(3)

The I/O chassis is in faulted mode as selected by switch 1 (the last stare switch) on the chassis backplane.