New and original Mitsubishi PLC FX3U-1PG or FX3U1PG

Mitsubishi FX3U-1PG | Single-Axis 200 kHz Pulse Output Positioning Module — FX3U / FX3UC / FX5U Compatible

Dedicated Pulse Output — One Module, One Axis, Up to 200 kHz

The FX3U-1PG is a special function block that adds one independent high-speed pulse output axis to a MELSEC FX3U or FX3UC PLC. The module generates pulse train outputs at up to 200 kHz for commanding servo motor drivers or stepping motor drivers — the same CW/CCW or PULSE+DIR format that motor drivers use as their motion command input.

Positioning logic runs inside the FX3U-1PG itself, not in the PLC's main CPU. The PLC writes position targets, speed profiles, and start commands to the module's buffer memory via 

FROM/TO instructions, and the module executes the positioning profile independently. This offloading matters: a 200 kHz pulse stream coordinated with the PLC's scan cycle would saturate the main CPU if handled natively. By delegating the pulse generation to dedicated hardware, the PLC remains free to manage its regular I/O scan and programme execution without interruption.

Up to 8 FX3U-1PG units can connect to one FX3U controller, providing up to 8 independent positioning axes from a single CPU — covering virtually all multi-axis motion applications within the FX3U platform.

Key Specifications

Servo and Stepper Motor Compatibility

The FX3U-1PG outputs a pulse train that commands any pulse-input servo driver or stepper motor driver. CW/CCW two-pulse mode or PULSE+SIGN (pulse plus direction) mode is selectable to match the connected driver's input format. Manual jog, zero-return, and automatic positioning operations are all configurable in the module's parameter set — the PLC writes the required operating mode and the module handles execution.

For multi-axis interpolated motion (linear interpolation between two or more axes), the FX3U-20SSC-H (SSCNET III interface) is the appropriate module. The FX3U-1PG handles single-axis independent motion; coordinated multi-axis interpolation is outside its scope.

FAQ

Q1: How does the FX3U-1PG communicate with the FX3U PLC?

The PLC CPU accesses the FX3U-1PG through FROM (read buffer memory) and TO (write buffer memory) instructions. The PLC writes positioning data — target positions, speeds, acceleration ramps, operation modes — to the module's buffer memory. The module reads this data and executes the positioning profile independently, updating the buffer with current position and status data that the PLC can read at any scan.

Q2: Can the FX3U-1PG be used with a stepper motor driver instead of a servo driver?

Yes. Any pulse-input driver is compatible — servo drivers and stepper motor drivers both accept the CW/CCW or PULSE+SIGN pulse train that the FX3U-1PG outputs. The module cannot receive encoder feedback directly; position counting from a servo encoder is handled by the servo driver's internal position loop, not the FX3U-1PG.

Q3: Up to how many FX3U-1PG modules can connect to one FX3U PLC?

Up to 8 FX3U-1PG units on a standard FX3U CPU, providing up to 8 independent positioning axes. On FX3UC PLCs, up to 6 units are supported. On FX5U (iQ-F) PLCs with FX3U-1PSU-5V power adapter, up to 8 units connect. The total special function unit count on the FX3U expansion bus must remain within the PLC's limit.

Q4: What is the difference between FX3U-1PG and FX3U-20SSC-H?

The FX3U-1PG outputs a pulse train for single-axis positioning of standard pulse-input servo or stepper drivers. The FX3U-20SSC-H uses SSCNET III fibre-optic interface to control Mitsubishi MR-J3 and MR-J4 series servo amplifiers with multi-axis interpolation. Use FX3U-1PG for single-axis applications with any pulse-input driver; use FX3U-20SSC-H for multi-axis interpolated motion with Mitsubishi servo amplifiers.

Q5: Does the FX3U-1PG retain positioning data after power loss?

The positioning data (table data, parameters) stored in the FX3U-1PG module is battery-backed in SRAM or stored in the FX3U PLC's own parameter memory, depending on the data type. Confirm the data retention arrangement from the FX3U-1PG user manual for the specific parameter types used in the application. Always maintain a GX Works backup of the FX3U programme and extension unit settings.