Technical Analysis: Mitsubishi FX2N-16MR Programmable Logic Controller

Executive Summary

The Mitsubishi FX2N-16MR is a compact, relay-output programmable logic controller (PLC) that has served as a workhorse in industrial automation systems since its introduction in the early 2000s. As part of the FX2N series—released in 1997 and discontinued in 2012—this 16-point I/O unit combines reliability, backward compatibility with earlier FX models, and sufficient processing power for small to medium-scale control applications. This technical analysis provides comprehensive specifications, compatibility information, application guidelines, and migration recommendations for engineers maintaining legacy systems or considering upgrade paths.

1. Technical Specifications

1.1 Core Parameters

1.2 Performance Specifications

• Processing Speed: 0.08 µs per basic instruction (6× faster than FX1N series)
• Memory Capacity: 8K steps built-in RAM (expandable to 16K with EEPROM memory cassette)
• Instruction Set: 27 basic instructions + 125 application instructions = 152 total
• Internal Devices:
• Auxiliary relays: 3,072 points (M0-M3071)
• Timers: 256 points (T0-T255)
• Counters: 235 points (C0-C234)
• Data registers: 8,000 points (D0-D7999)
• High-Speed Counter: 8 points maximum
• Single-phase: 60kHz (2 points), 10kHz (4 points)
• Two-phase: 30kHz (1 point), 5kHz (1 point)
• Pulse Output: Not built-in (requires special function module like FX2N-1PG)
• Communication: Built-in RS-422 programming port (requires expansion boards for RS-232/RS-485)

1.3 Environmental Specifications

Source: Mitsubishi Electric FX2N Series Technical Specifications [1]

2. Compatibility Information

2.1 Expansion Capabilities

The FX2N-16MR maintains full backward compatibility with earlier FX series modules while supporting extensive expansion:

I/O Expansion Modules:
– Input Modules: FX2N-16EX (16 points), FX2N-8EX (8 points)
– Output Modules: FX2N-16EYR (16 relay points), FX2N-8EYR (8 relay points)
– Mixed I/O: FX0N series modules via adapter

Special Function Modules (Maximum 8 modules total):
– Analog I/O: FX2N-4AD (4-channel input), FX2N-4DA (4-channel output)
– Temperature Control: FX2N-4AD-PT (Pt100), FX2N-4AD-TC (thermocouple)
– Positioning: FX2N-1PG (1-axis pulse generator)
– Communication: FX2N-232IF (RS-232), FX2N-485-BD (RS-485)
– High-Speed Counter: FX2N-1HC (50kHz 1-phase or 2-phase counter)

2.2 System Configuration Limits

• Maximum I/O Points: 256 points (with expansion units and modules)
• Maximum Expansion Modules: 8 special function modules
• Power Supply Capacity: 460mA DC24V output for sensors (250mA for 16/32 I/O units)
• Program Memory: 16K steps maximum with EEPROM memory cassette

2.3 Peripheral Compatibility

• Programming Software: GX Developer (older version), compatible with FX-GP/WIN
• Programming Devices: FX-20P, FX-10P, personal computer with RS-422 adapter
• HMI Connectivity: Supports Mitsubishi GOT series, third-party HMIs via communication modules
• Network Protocols: CC-Link, DeviceNet, Profibus (requires appropriate master/slave modules)

Source: Mitsubishi FX2N Series Expansion Manual [2]

3. Application Guidelines

3.1 Typical Application Scenarios

The FX2N-16MR is suitable for small-scale automation applications where relay output provides flexibility for mixed AC/DC loads:

1. Small Machinery Control
2. Packaging machines with sequential valve control
3. Labeling equipment with sensor inputs and actuator outputs
4. Simple conveyor systems with photo-sensor detection
5. Building Automation
6. Lighting control systems (relays suitable for AC lighting circuits)
7. Access control with door sensors and magnetic locks
8. HVAC equipment sequencing for small facilities
9. Laboratory Equipment
10. Test bench automation with mixed signal types
11. Process sequencing with timer/counter functions
12. Data logging capabilities through communication modules
13. Peripheral Device Coordination
14. Integration with sensors, pushbuttons, and pilot lights
15. Coordination of multiple small actuators (solenoids, small motors)
16. Interface with older equipment requiring relay isolation

3.2 Wiring and Installation

Power Supply Connection:

AC Power (100-240V) → L (Line) / N (Neutral) terminals
Protective Earth → ⏚ (Ground) terminal

Input Circuit Wiring (Sink Configuration):

DC24V (+) → Sensor/switch → Input terminal (X0-X7)
Input terminal → COM (common) → DC24V (-)

Output Circuit Wiring (Relay Contacts):

Load Power Source (AC/DC) → Output terminal (Y0-Y7)
Output terminal → Load → Return to load power source

Critical Installation Notes:
– Use dedicated grounding with resistance <100Ω
– Separate high-voltage and control wiring (minimum 100mm spacing)
– Install surge suppressors for inductive loads (RC networks for AC, diodes for DC)
– Observe DIN rail mounting torque: 0.5-0.6 N·m
– Maintain minimum clearance: 50mm above and below unit for heat dissipation

3.3 Programming Considerations

Memory Allocation Strategy:
– Reserve data registers D0-D199 for frequently accessed variables
– Use auxiliary relays M8000-M8255 for system flags and status
– Implement subroutine structures for complex logic (CALL, SRET)

Performance Optimization:
– Place frequently executed logic near program start
– Use application instructions for complex operations (vs. ladder logic equivalents)
– Implement constant scan mode for time-critical applications

Troubleshooting Common Issues:

Source: FX2N Series Programming Manual [3]

4. Migration and Alternative Recommendations

4.1 Direct Replacement Options

With the FX2N series officially discontinued since 2012, several migration paths exist:

1. FX3U Series (Recommended for Similar Applications)
– Model: FX3U-16MR/ES
– Advantages:
– 3× faster processing (0.065µs/basic instruction)
– Built-in high-speed counters and pulse outputs
– Support for both sink and source inputs
– Enhanced communication capabilities
– Considerations: Program migration required, some expansion modules may need replacement

2. FX5U Series (For Future-Proof Upgrades)
– Model: FX5U-32MR/ES
– Advantages:
– 10× faster processing than FX2N
– Built-in Ethernet and USB ports
– Support for advanced motion control
– IEC 61131-3 programming standards
– Considerations: Complete system redesign recommended, not drop-in replacement

4.2 Alternative Models Within FX2N Family

For different I/O requirements while maintaining compatibility:

4.3 Migration Planning Checklist

1. Inventory Existing System
2. Document all I/O points and their functions
3. List all expansion modules and special function blocks
4. Record program memory usage and complex instructions
5. Evaluate Technical Requirements
6. Verify new processor meets speed requirements
7. Confirm I/O compatibility (sink vs. source considerations)
8. Check communication protocol support
9. Plan Migration Steps
10. Create backup of existing program and parameters
11. Develop test plan for migrated system
12. Schedule downtime for hardware replacement
13. Consider Long-Term Strategy
14. Assess future expansion needs
15. Evaluate maintenance part availability
16. Plan for eventual transition to newer platforms

Source: Mitsubishi Electric Migration Guide [4]

5. Technical Comparison with Successor Models

6. Maintenance and Lifecycle Considerations

6.1 Critical Components and Lifespan

• Relay Contacts: Mechanical life ≈ 10 million operations, electrical life ≈ 100,000 operations (at rated load)
• Backup Battery (F2-40BL): Typical lifespan 5 years (preserves program memory and clock)
• Electrolytic Capacitors: Expected life 10-15 years (depends on operating temperature)

6.2 Preventive Maintenance Schedule

6.3 End-of-Life Planning

Given the FX2N series reached end-of-production in 2012 and end-of-service in 2019:

1. Immediate Actions:
2. Secure spare units for critical replacements
3. Document complete system specifications
4. Develop migration timeline
5. Medium-Term Strategy (1-3 years):
6. Identify suitable replacement platforms
7. Begin pilot migration projects
8. Train maintenance personnel on new systems
9. Long-Term Planning (3-5 years):
10. Complete system migration
11. Phase out remaining FX2N components
12. Update maintenance procedures

7. Conclusion

The Mitsubishi FX2N-16MR represents a significant chapter in industrial automation history, offering reliable control for countless small-scale applications over two decades. While its production has ceased, understanding its specifications, compatibility, and migration options remains crucial for engineers maintaining legacy systems.

For new projects, the FX3U or FX5U series provide superior performance, enhanced features, and long-term support. However, for existing systems where replacement isn’t immediately feasible, proper maintenance and understanding of the FX2N-16MR’s capabilities can ensure continued reliable operation.

The transition from legacy PLCs to modern platforms represents both a technical challenge and an opportunity to embrace enhanced functionality, connectivity, and future-proof automation solutions.

8. References

1. Mitsubishi Electric Corporation. (2023). FX2N Series Technical Specifications. [Online] Available at: https://www.mitsubishielectric.co.jp/fa/products/faspec/detail.do?kisyu=/plc_fx&formNm=640058014
2. Mitsubishi Electric Corporation. (2025). FX2N to FX3U Migration Guide. [Online] Available at: https://www.mitsubishielectric.co.jp/fa/products/cnt/plc_fx/ex/renew/close/discon_1.htm
3. PLC Products. (2025). Mitsubishi FX2N-16MR Technical Documentation. [Online] Available at: https://plcproducts.com/mitsubishi/modules/programmable_controller/fx2n-16mr
4. Mitsubishi Electric Americas. (2025). FX2N/FX2NC Series Legacy Information. [Online] Available at: https://us.mitsubishielectric.com/fa/en/support/parts/legacy-products/programmable-controllers/fx2n-fx2nc
5. Automation Jaya. (2019). Mitsubishi PLC FX2N Series Technical Comparison Tables. [Online] Available at: https://www.automationjaya.com/2019/06/mitsubishi-plc-fx2n-series.html
6. International Electrotechnical Commission. (2013). IEC 61131-3: Programmable controllers – Part 3: Programming languages.
7. Mitsubishi Electric Corporation. (2020). GX Works2 Programming Manual.