IDEC FC6A MicroSmart — ERR LED & Error Codes

IDEC · beginner · 20 min

When an IDEC FC6A MicroSmart lights its ERR LED, the cause is stored as an error code you read and clear in WindLDR. Learn the common ones — watchdog timeout, program syntax, data link and corrupted ROM — and how to fix each rather than just clearing it.

ℹ️ On an FC6A MicroSmart the ERR LED means the CPU logged an error code. Read and clear it in WindLDR. The fix depends on the code — a program syntax error clears itself when you download a correct program, but a repeating watchdog error means the unit is failing.

The ERR LED points to a stored code

The IDEC FC6A MicroSmart stores fault information as error codes (in special data registers) and signals a problem on its ERR LED. You read — and clear — those codes with WindLDR, the FC6A programming and diagnostic software. So the workflow is always: see ERR, connect WindLDR, read the code, fix the cause, clear the code. Here are the common causes and their correct actions.

Watchdog timer error

A watchdog timer error means a scan ran too long. Clear the error code using WindLDR — but treat frequency as the real signal: if this error occurs frequently, the FC6A has to be replaced. A one-off may be transient; a repeating watchdog error is failing hardware.

User program syntax error

If the user program has a syntax error, correct the program and download the corrected version. The error code clears automatically when a correct user program is transferred — you don't clear it by hand, you fix the program.

Data link problems

If the data link function area settings are wrong or the cable isn't connected correctly, correct the data-link settings or fix the cable, then turn the power off and on, or initialize the data link. This is the one where a wiring/topology mistake masquerades as a CPU fault.

Corrupted ROM program

If the user program stored in the FC6A ROM is corrupted, download a correct user program and clear the error in WindLDR. A related case is a memory backup failure: data designated to be retained through a power failure gets corrupted — restore/redownload and clear.

Step-by-step

1. ERR LED on → connect WindLDR and read the error code and description.
2. Watchdog timeout? Clear it; if it keeps returning, replace the FC6A.
3. Program syntax error? Correct the program and download — the code clears on a good transfer.
4. Data link error? Fix the data-link settings or cable, then power-cycle or initialize the data link.
5. Corrupted ROM / backup failure? Download a known-good program and clear the code.
6. Confirm the ERR LED is off and the CPU runs.

Never do this

Don't just keep clearing a recurring watchdog or ROM error to keep the line up — IDEC's own guidance is that a frequently-recurring watchdog error means the unit must be replaced. Running a machine on a CPU that faults unpredictably is the real hazard; swap it.