Comprehensive Guide to Mitsubishi PLC Instructions: Master All Series in One Place
Comprehensive Guide to Mitsubishi PLC Instructions: Master All Series in One Place
In the field of industrial automation, Mitsubishi PLCs (Programmable Logic Controllers) are widely adopted for their robust functionality and high reliability. This article provides a detailed breakdown of key Mitsubishi PLC instructions, including:
Load and Output Instructions
Contact Series and Parallel Connection Instructions
Block Operation Instructions
Set and Reset Instructions
Pulse Differential Instructions
Master Control Instructions
Stack Instructions
Invert/No Operation/End Instructions
Step Ladder Instructions
Enabling comprehensive mastery of Mitsubishi PLC programming.
I. Load and Output Instructions
LD (Load Instruction): Connects a normally open (NO) contact to the left power rail. Mandatory for logic lines starting with an NO contact.
LDI (Load Inverse Instruction): Connects a normally closed (NC) contact to the left power rail. Mandatory for logic lines starting with an NC contact.
LDP (Load Rising Edge Instruction): Detects the OFF→ON transition of an NO contact connected to the left power rail (activates for one scan cycle).
LDF (Load Falling Edge Instruction): Detects the ON→OFF transition of an NC contact connected to the left power rail.
OUT (Output Instruction): Drives a coil (output element).
Usage Notes:
LD/LDI can connect to the left power rail or combine with ANB/ORB for block logic operations.
LDP/LDF maintain activation for one scan cycle only upon valid edge detection.
Target elements for LD/LDI/LDP/LDF: X, Y, M, T, C, S.
OUT can be used consecutively (equivalent to parallel coils). For timers (T) and counters (C), specify constant K or a data register after OUT.
Target elements for OUT: Y, M, T, C, S (not X).
II. Contact Series Connection Instructions
AND: Series-connects an NO contact (logical AND).
ANI (AND Inverse): Series-connects an NC contact (logical AND-NOT).
ANDP: Rising-edge detection series connection.
ANDF: Falling-edge detection series connection.
Usage Notes:
AND/ANI/ANDP/ANDF support unlimited consecutive series connections.
Target elements: X, Y, M, T, C, S.
Example: OUT M101 followed by AND T1 driving Y4 is a "continuous output."
III. Contact Parallel Connection Instructions
OR: Parallel-connects an NO contact (logical OR).
ORI (OR Inverse): Parallel-connects an NC contact (logical OR-NOT).
ORP: Rising-edge detection parallel connection.
ORF: Falling-edge detection parallel connection.
Usage Notes:
Left ends connect to LD/LDI/LDP/LPF; right ends link to the previous instruction’s right end. Unlimited parallel uses.
Target elements: X, Y, M, T, C, S.
IV. Block Operation Instructions
ORB (OR Block): Parallel connection of two or more series contact circuits.
ANB (AND Block): Series connection of two or more parallel contact circuits.
Usage Notes:
Each series circuit block in ORB must start with LD/LDI.
Each parallel circuit block in ANB must start with LD/LDI.
Limit of 8 consecutive ORB/ANB instructions.
V. Set and Reset Instructions
SET: Activates and latches the target element.
RST: Deactivates and clears the target element.
Usage Notes:
SET targets: Y, M, S.
RST targets: Y, M, S, T, C, D, V, Z. Clears data registers (D,Z,V) and resets latched timers/counters.
Last-executed SET/RST for a given element takes precedence.
VI. Pulse Differential Instructions
PLS (Pulse Rising Edge): Generates one scan-cycle pulse on OFF→ON transition.
PLF (Pulse Falling Edge): Generates one scan-cycle pulse on ON→OFF transition.
Usage Notes:
Targets: Y, M.
PLS: Active for one scan cycle after driving input turns ON.
PLF: Active for one scan cycle after driving input turns OFF.
VII. Master Control Instructions
MC (Master Control): Connects common series contacts. Shifts the left power rail position.
MCR (Master Control Reset): Resets MC, restoring the original left power rail.
Usage Notes:
Targets: Y, M (not special relays).
MC requires 3 program steps; MCR requires 2.
The master control contact is a vertical NO contact connected to the left power rail. Contacts below it must start with LD/LDI.
When MC input is OFF: Latched timers/counters and SET/RST-driven elements retain state; non-latched timers/counters and OUT-driven elements reset.
Supports 8-level nesting (N0–N7). Reset with MCR in reverse order.
VIII. Stack Instructions
MPS (Push Stack): Stores operation result to stack top.
MRD (Read Stack): Reads top value without removal.
MPP (Pop Stack): Reads top value and removes it.
Usage Notes:
Target elements: None (stack only).
MPS and MPP must be paired.
Maximum stack depth: 11 levels.
IX. Invert, No Operation & End Instructions
INV (Invert): Inverts the preceding logic result. Cannot connect to power rail or standalone.
NOP (No Operation): Empty instruction (occupies one step). Used for temporary deletions.
END (End): Terminates program execution. Reduces scan cycle time.
Usage Notes:
Use END during debugging to isolate program sections.
X. Step Ladder Instructions
STL (Step Ladder Contact): Activates step control with state relay S (e.g., STL S200).
RET (Return): Exits step ladder and returns to main program.
State Transition Diagram:
Sequential processes divide into states (steps), each performing unique actions.
Transition occurs when conditions (e.g., X1=ON) are met.
Each state defines:
Output actions
Transition condition
Next-state target (e.g., S20 → S21).