PS001

Navigate to SYSTEM > PARAM and verify Parameter 0100 (I/O channel settings). Bit 4 sets parity enable (0=disabled, 1=enabled), Bit 5 sets even/odd parity (0=odd, 1=even).

Check Parameter 0101 (baud rate), Parameter 0102 (stop bits). Ensure these match the external device settings exactly. Common settings: 9600 baud, 7 data bits, even parity, 2 stop bits for tape readers.

Verify Parameter 0020 bit 0 (TV check) is set correctly. If set to 1, vertical parity checking is enabled for tape input which may cause false parity errors if the device doesn't support it.

Test with known-good settings: Set P0100 to even parity enabled, P0101 to 4800 or 9600 baud, and retry communication. Consult peripheral device manual for required parity configuration.

Inspect RS-232C cable at both CNC and peripheral ends. Check for bent pins on DB9 or DB25 connectors, ensure connector backshell is tight, and verify cable shield is properly grounded at CNC end only.

Verify proper wiring: Pin 2 (TXD from CNC) to Pin 3 (RXD on device), Pin 3 (RXD on CNC) to Pin 2 (TXD on device), Pin 5 (GND) to Pin 5 (GND). Confirm crossover vs straight-through cable matches device requirements.

Replace RS-232C cable with known-good cable, maximum 15 meters length, using shielded twisted-pair cable to minimize electrical noise. Test communication after replacement.

Check DIAGNOSIS > I/O or DIAGNOSIS > SERIAL screen to monitor RXD/TXD signal activity during communication attempt. Absence of signals indicates cable or hardware failure.

Test with an alternate peripheral device (PC with terminal software, different tape reader, or DNC system) using identical parameter settings. If alarm clears, original peripheral is faulty.

Check peripheral device power supply and status indicators. For tape readers, clean optical sensors and verify tape feed mechanism operates smoothly without jamming or skipping.

Navigate to SYSTEM > DIAGNOSIS > I/O and observe diagnostic numbers related to serial communication (specific numbers vary by control series). Look for persistent error counts incrementing during transmission attempts.

If all external devices fail with PS001, suspect CNC main board serial port failure. Contact Fanuc service to test/replace main board or I/O interface board. Verify JD1A/JD1B connector seating on main PCB.

Power down CNC before inspecting internal circuit boards. ESD precautions required when handling PCBs.