Mitsubishi PLC Reference

The reference covers all fundamental Mitsubishi ladder instructions: LD/LDI (start with NO/NC contact), AND/ANI (series NO/NC contact), OR/ORI (parallel NO/NC contact), OUT (bit output), SET/RST (latch set/reset that holds state), PLS (rising edge one-scan pulse), PLF (falling edge one-scan pulse), ANB (series connection of two parallel blocks), and ORB (parallel connection of two series blocks). Each instruction includes syntax and practical ladder examples.

Timers use T devices with a preset value in the specified time base. Standard timers (T0-T199) have 100ms resolution, so OUT T0 K50 creates a 5-second timer (50 x 100ms). High-speed timers (T200-T255) operate at 1ms resolution for precision timing. Timers count up while their input condition is ON and turn ON their contact when reaching the preset. The STMR instruction provides special timing patterns including delayed ON, delayed OFF, one-shot, and flicker outputs.

Mitsubishi FX series uses octal numbering for input (X) and output (Y) devices. This means digits only go from 0 to 7: X0-X7 form the first byte, X10-X17 the second byte, X20-X27 the third, and so on. There is no X8 or X9. This octal convention matches the physical I/O wiring groups of 8 points per module. Internal devices (M, D, T, C) use standard decimal numbering.

Special relays (M8000-M8255) provide system status and control functions. Key examples: M8000 is always ON during RUN mode (useful as a constant TRUE contact), M8002 turns ON for exactly one scan at power-on/RUN start (for initialization routines), M8012 provides a 100ms clock signal for blinking indicators. These special relays are read-only system flags that reflect PLC operating conditions.

CMP D0 K100 M0 compares the value in D0 against the constant 100 and sets three consecutive result bits: M0 turns ON if D0 > 100 (greater than), M1 turns ON if D0 = 100 (equal), and M2 turns ON if D0 < 100 (less than). This three-bit result pattern allows direct branching for all comparison outcomes in subsequent ladder rungs without needing additional comparison instructions.

MOV transfers a 16-bit value (range -32768 to +32767) between registers, such as MOV K100 D0 to store 100 in D0. DMOV transfers a 32-bit value (range -2147483648 to +2147483647) and uses two consecutive registers, such as DMOV D0 D100 which transfers the 32-bit value from D0-D1 to D100-D101. Use DMOV when values exceed the 16-bit range or when working with 32-bit arithmetic results from DMUL or DDIV instructions.

CC-Link configuration requires setting the master station number (typically 1) and defining remote device ranges: RX (remote inputs, e.g., X1000~), RY (remote outputs, Y1000~), RWr (remote read registers, D1000~), and RWw (remote write registers, D1100~). Each slave module occupies a station number with a specified number of occupied stations (e.g., 4). The master polls all slaves cyclically for real-time remote I/O data exchange.

FROM reads data from a special function module's buffer memory into PLC data registers, and TO writes PLC data to the module's buffer memory. Syntax: FROM H0 K0 D0 K1 reads 1 word from slot 0, buffer address 0 into D0. TO H0 K1 D10 K1 writes D10 to slot 0, buffer address 1. These instructions are essential for communicating with analog input/output modules, positioning modules, and communication modules that have their own internal buffer memory.