Mitsubishi FXo/FXon PLC Hardware Practice

When using Y0 as the pulse train output (PLSY command) or Y1 as the PWM output, due to the fast switching speed required by the internal circuit, an external pull-up resistor (1-2k Ω) must be connected to ensure that the output current is ≥ 0.2A, otherwise waveform distortion may cause the stepper motor to lose step.

Install 1-2A fuses every 4 output points.

Extended configuration rules (FXon only)

The FXon system connects expansion units and modules through the CPU bus and must comply with the following restrictions:

FXo is not extensible. FXon's MPU (Basic Unit) can connect up to:

Two special functional modules (such as FXon-3A analog, FXon-16NT network module), or

Expansion blocks with no more than 32 I/O points (such as two 16 point expansion blocks or four 8-point expansion blocks).

The total system I/O points (including basic units and extensions) shall not exceed 128 points.

FXon-24Mx basic unit: Physically only has 14 inputs/10 outputs, but occupies 16 inputs/16 outputs of system I/O, so when calculating the remaining expandable points, it must be deducted by 32 points.

FXon-8ER-ES/UL (4 inputs and 4 outputs) actually occupies 16 I/O points (8 inputs and 8 outputs).

The FXon-485ADP communication adapter can only be used for basic units with CPU version ≥ 1.2.

Maximum length of extension cable: When using FXon-65EC (650mm), the entire system can only use one of these cables. Can the distance between two layers exceed 650mm? It is recommended not to exceed it in practice.

Diagnosis and fault codes

There are four LEDs on the device panel: POWER (green), RUN (green), ROG. E (red), and CPU-E (red). By combining special registers and error flags, most hardware and software faults can be located.

7.1 Preliminary investigation process

Check in the following order according to the table:

Normal result of step operation

Measure the voltage of the power terminal AC or DC within the allowable range

2. Check if all wiring terminals are tightened and not loose

After powering on, if the POWER LED is on or off, check if the 24V load is too high or if the internal fuse is blown

Download the empty test program and force the RUN LED to light up. The output can be manually set

5. Observe that PROG. E/CPU. E should not be constantly on or flashing

7.2 Error Code Interpretation

ROG. E flashing: Program syntax error, parameter error, or execution error (such as watchdog timeout). Connect programming software to view error codes in D8065~D8067.

CPU. E constantly on: hardware failure or crash. Common reasons:

The FXon memory card can be unplugged and unplugged while powered on (retry after power failure to recover).

The program scanning time is too long, exceeding the watchdog setting (D8000 default 200ms). Check the maximum scanning time of D8012. If it is greater than D8000, adjust the D8000 value or optimize the program.

Error code table (D8061 hardware error, D8063 communication error):

Code meaning

6101 RAM Error

6102 operation circuit error

6301 Communication parity/overflow/frame error

6305 instruction error

6306 communication watchdog timeout

7.3 Common special relays (M) and registers (D)

Component function

M8000 RUN monitoring is always on

M8002 initial pulse

M8004 error occurred (D8004 storage error M number)

M8035~M8037 forced RUN/STOP control

M8039 Constant Scan Enable

M8061 PC hardware error flag

M8067 program execution error flag

D8000 watchdog timer setting value

D8001 PLC type version

D8012 maximum scanning time

D8067 execution error code

Battery replacement (FXon-40B, FXon only)

The FXon series can be optionally equipped with a real-time clock memory card (FX-RTC), which relies on the FXon-40B battery to maintain clock operation when the host loses power. The battery is a non rechargeable lithium battery with a lifespan of approximately 4 years (storage period of 1 year).

Replacement steps:

Cut off all power to the PLC.

Uncover the cover plate labeled "MITSUBISHI" at the top.

Expose the small circuit board socket on the left side of the memory card slot and remove the fixing clip.

Unplug the old battery and replace it with a new one within 20 seconds, otherwise the real-time clock data will be lost.

Reinstall the fixing clip and cover plate.

Attention: If the real-time clock card is not installed, this battery is useless.

Programming and Communication Ports

The basic unit comes with a programming port (RS422 round or rectangular 8-pin), which can be connected to a handheld programmer (FX-20P-E) or a computer through an SC-09 adapter.

FXon-232ADP or FXon-485ADP can be installed on the left side of the basic unit, occupying 8 I/O points and providing RS232 or RS485 communication channels for connecting to the upper computer, HMI, or frequency converter. Note: After installing the communication adapter, no other expansion blocks can be added on this side.

Common installation errors and remedies

Root cause solutions for error phenomena

After power on, the POWER light does not light up and the internal input fuse is blown; 24V service power overload, disconnect the 24V load and try again; If it still doesn't light up, return to the factory for repair

Input signal is correct but PLC cannot detect S/S terminal wiring error; Correct the S/S connection based on Sink/Source if the input response time does not match the signal pulse width; Adjust the digital filtering time to be less than the signal width