1. Classification System of Logic Operation Instructions
1. Basic Logic Instructions
AND Logical AND Multi-condition alarm (Pressure + Temperature > Threshold)
OR Logical OR Any fault triggers shutdown
XOR Logical XOR Parity check
INV Negation operation Inversion of sensor signal
2. Bit Operation Instructions
BSET Bit Set Individually control the status of a device
BRST Bit Reset Clear alarm flag
BTR Bit Read Diagnose specific bits in the register
3. Block Logic Instructions
ANB Block AND Combine multiple contact groups
ORB Block OR Parallel logic branches
2. Core Instruction Practical Cases
Case 1: Equipment Safety Interlock System
Control Requirement: The motor can only start (Y0) when the protective cover is closed (X0) and the emergency stop has not been triggered (X1)
LD X0 // Protective cover closed
AND X1 // Emergency stop not triggered
OUT Y0 // Motor start
Logical Expression: Y0 = X0 AND X1
Case 2: Multi-Fault Alarm System
Control Requirement:
– Trigger alarm (Y1) when temperature is too high (X2) or pressure is too low (X3)
LD X2 // Temperature too high
OR X3 // Pressure too low
OUT Y1 // Alarm output
Logical Expression: Y1 = X2 OR X3
Case 3: Parity Check System
Control Requirement:
Perform parity check on 8-bit data D100
Set Q0 for odd parity, set Q1 for even parity
LD X4 // Check start signal
XOR D100 K1 D200 // XOR 1 to get parity bit
AND D200 K1
OUT Y2 // Odd parity flag
AND D200 K0
OUT Y3 // Even parity flag
1. Calculate parity bit using XOR instruction
2. Use AND instruction to extract check result
Case 4: Equipment Status Monitoring System
Control Requirements: 1. Real-time monitoring of the operating status of 8 devices (X10-X17); 2. When any device fails, the total fault light Y4 flashes
LD X10
OR X11
OR X12
OR X13
OR X14
OR X15
OR X16
OR X17
OUT M0 // Total fault signal
LD M0
OUT Y4 // Fault light stays on
LD M8013 // 5-second pulse
AND M0
OUT Y4 // Overlay flashing effect
Optimization Points:
1. Use OR instruction to combine multiple inputs
2. Achieve flashing effect through dual output
3. Advanced Application Techniques
1. Simplifying Complex Logic
// Original logic: (A+B)*(C+D)
LD A
OR B
LD C
OR D
ANB
OUT Y
2. Individual Bit Control
// Individually control the 3rd bit (Y2)
BSET Y2 // Set
BRST Y2 // Reset
3. Register Bit Status Monitoring
// Monitor if the 5th bit of D100 is 1
BTR D100 K5 M10 // Read D100.5 to M10
4. Common Problems and Solutions
Problem 1: Logic result does not match expectations
Cause: Incorrect contact order leading to priority changes
Solution: Use parentheses to clarify operation order (ANB/ORB instructions)
Problem 2: Bit operation instructions ineffective
Cause: Target bit exceeds range (FX3U maximum Y177)
Solution: Check if bit element number is within the allowed range
Problem 3: Block logic instruction error
Cause: ANB/ORB usage exceeds 8 times
Solution: Write logic in segments, add intermediate relays
5. Pitfall Guide
⚠️ Prohibited Actions:
1. Cannot directly use INV instruction on bit elements (X/Y/M/S)
2. Block logic instructions (ANB/ORB) must immediately follow contact groups
3. Bit operation instructions (BSET/BRST) cannot be used on word elements
💡 Optimization Tips:
1. Use intermediate relays (M) to simplify complex logic
2. Add comments to critical logic (e.g., // Safety interlock conditions)
3. Display bit status on touch screens (e.g., M10-M17)
Next Issue Preview:
“Mitsubishi PLC Shift Operation Instructions in Practice” – From LED flowing lights to password encryption, a hands-on guide to mastering data bit movement! Follow↓↓
Unlock the black technology of bit operations~
(End of article interaction: What logic operation instructions have you used in your projects? What logical errors have you encountered? Share solutions in the comments!)