Mitsubishi MELSEC Compatibility Matrix

Compatibility Overview

The Mitsubishi Electric MELSEC series has served as a cornerstone of industrial automation for decades. However, navigating the physical, electrical, and protocol compatibility across generation jumps—such as legacy AnS/QnAS to legacy Q-Series, and classic Q-Series to the modern iQ-R and iQ-F Series platforms—presents significant engineering challenges.

Mitsubishi’s design philosophy emphasizes preservation of legacy application code and wiring investments while adapting to modern, deterministic communication standards like CC-Link IE TSN, EtherNet/IP, PROFINET, and EtherCAT. Achieving seamless integration requires a clear understanding of backplane interfaces, firmware versions, memory mapping configurations, and software engineering environments (GX Developer, GX Works2, and GX Works3).

Supported Models

Mitsubishi MELSEC PLCs are divided into several key families, each designed for specific performance tiers, from micro-PLC applications to highly distributed, high-speed processes.

MELSEC iQ-R Series (Flagship Modular)

Engineered for high-speed, multi-discipline automation. Key CPUs include the R04CPU, R08CPU, R16CPU, and the high-capacity R120CPU. The platform supports native multi-CPU configurations, safety control, and integrated motion synchronization.

MELSEC Q Series (Modular)

The legacy workhorse of the MELSEC family. Standard models like the Q03UDECPU, Q06UDVCPU, and high-speed process CPUs such as the Q12HCPU are widely deployed. Although older, many systems remain active or function as remote I/O stations in modern topologies.

MELSEC iQ-F Series (Compact)

The successor to the FX series (specifically FX3U). Key processors include the FX5U-32MR/ES and FX5UC-32MT/D. This platform features built-in Ethernet, analog I/O, and specialized positioning control without requiring an expansion backplane.

MELSEC L Series (Rack-Free Modular)

An intermediate, rack-free modular design ideal for field-level control. Key models include the L02CPU and L26CPU-BT, featuring an integrated CC-Link or Ethernet port on the processor unit.

Hardware Compatibility & Software Support Matrix

Unsupported Models

As components age, maintaining obsolete architectures becomes highly critical due to component degradation and limited support interfaces. The following families are legacy or End-of-Life (EOL), requiring active migration planning:

• MELSEC AnS/QnAS Series (Obsolete): Processors such as the A1SJHCPU and A2USHCPU are fully retired. These units rely on obsolete 5V TTL backplanes and outdated serial protocols.
• MELSEC FX1N / FX2N Series (Obsolete): Replaced by the FX3U, and subsequently the iQ-F series. These microprocessors lack security protocols, modern network stacks, and modern workspace integration.
• MELSEC FX3U Series (Deprecated/EOL): While widely deployed (e.g., FX3U-32MR/ES), these models have reached end-of-life status. Direct engineering replacements should target the FX5U platform.

To bridge the gap between unsupported legacy chassis and modern architectures, special migration hardware must be deployed. For instance, the QA61B expansion base allows Q-Series processors to read and write to existing AnS expansion racks, preserving installed digital and analog field wiring before a complete hot-swing upgrade.

Communication Options

Mitsubishi PLCs support a wide range of industrial communication protocols. Fieldbus integration depends heavily on the communication module selected and the system architecture.

• CC-Link IE TSN (Time-Sensitive Networking): The modern standard for iQ-R systems. Utilizing the RJ71GN11-T2 master/local module, it combines gigabit Ethernet communication with synchronization cycle times under 31.25 microseconds, bringing real-time deterministic control to servo and remote I/O nodes.
• CC-Link IE Field / Control: Gigabit industrial Ethernet designed for high-volume data transmission. Supported via modules like the QJ71GP21-SX (for Q Series) and RJ71GF11-T2 (for iQ-R Series).
• EtherNet/IP: Commonly required for interfacing with third-party drives, HMIs, and remote I/O blocks. Supported natively on select iQ-R and iQ-F CPUs, or via specialized communications modules such as the QJ71EIP71 (for Q Series) and RJ71EN71 (for iQ-R).
• PROFINET: Integrated using communication master/slave modules. For the Q-Series, the QJ71PN92 serves as a PROFINET IO Controller, whereas iQ-R systems use the RJ71PN92 module to join PROFINET RT networks.
• Modbus TCP / RTU: Native inside the iQ-F (FX5U) network port. For modular systems, the QJ71MT91 (Q Series Modbus TCP) or the RJ71C24 (iQ-R Serial for Modbus RTU) provide quick configuration pathways for third-party instruments.
• EtherCAT: Implemented via dedicated network master modules like the RJ71EC91, enabling the iQ-R system to command EtherCAT servo drives and bus-coupler I/O terminals.

Integration Notes

Successful integration of hybrid Mitsubishi MELSEC systems depends on precise hardware orientation and software routing configuration.

Coexistence of Q and iQ-R Modules

You cannot physically plug an iQ-R module (e.g., RJ71GF11-T2) into a standard Q-Series base unit (Q38B). However, you can populate a Q-Series module (e.g., QJ71GP21-SX) on an iQ-R system by utilizing an RQ68B or RQ612B extension base unit. The RQ base translates the internal bus signaling. Note that the main base must always run a native iQ-R CPU (e.g., R08CPU).

Software Project Migration

When translating projects from GX Works2 (Q-Series) to GX Works3 (iQ-R Series), absolute address offsets (e.g., D100, M200) can be imported directly. However, special relays (SM) and special registers (SD) are completely different between Q and iQ-R architectures. Developers must run the standard project conversion utility in GX Works3 and manually resolve unresolved compiler errors related to system flags.

Firmware Dependencies

To run modern protocols like CC-Link IE TSN on iQ-R platforms, the CPU modules must meet minimum hardware functional versions and firmware revisions. Ensure that R-series CPU firmware is updated to Version 40 or higher to prevent communication dropouts on TSN segments with high broadcast congestion.

Common Compatibility Issues

• Buffer Memory Mappings: Legacy communication or analog modules (e.g., Q64AD) have static buffer memory configurations. When converting programs or importing module parameters into an iQ-R project via an RQ extension rack, verify that read/write commands (FROM/TO instructions or direct buffer memory access U*\G*) are calculated to point to the correct slot offset.
• Backplane Current Draw Constraints: High-density modules or communications processors (like the RJ71EN71) pull significant 5V DC current from the base unit. In hybrid RQ base configurations, verify that the system power supply (e.g., R61P or R62P) can handle the combined load of the legacy Q modules and modern interface cards.
• CC-Link Version Incompatibilities: Combining standard CC-Link v1.10 devices with CC-Link v2.00 master stations (e.g., QJ61BT11N) on the same segment is supported, but the entire network will default to the lowest common denominator for cyclic transmission times. Be sure to match station mapping variables in the parameter section.
• Double-Type Real Math Shifts: Modifying CPU models from FX3U to FX5U can cause unexpected math syntax discrepancies. The FX3U limits floating-point accuracy differently than the modern ARM-based processor in the FX5U, meaning precision equations must be verified to prevent data register overflows.

FAQ

Q: Can I use Q-Series I/O modules directly on an iQ-R main base unit?

No. The physical connector alignments, bus logic, and voltage tolerances differ. You must use an RQ-type extension base (such as the RQ68B or RQ612B) connected via an RC06B or RC12B extension cable to the iQ-R main base unit. This allows Q-series digital, analog, and network modules to run seamlessly under an iQ-R CPU control loop.

Q: Which software package do I need to program a hybrid MELSEC system containing both Q and iQ-R PLCs?

You will need the complete iQ Works software suite, which bundles both GX Works2 (for Q and L Series PLCs) and GX Works3 (for iQ-R and iQ-F Series PLCs). If you program a hybrid system where Q-series modules are on an RQ extension rack controlled by an iQ-R CPU, the entire configuration is engineered within GX Works3.

Q: Does the FX5U (iQ-F) PLC support legacy FX3U expansion modules?

Yes, but not directly. You must install a FX5-CNV-BUS or FX5-CNV-BUSC bus conversion module on the FX5U chassis. This hardware adapter converts the newer high-speed iQ-F bus signaling format down to the legacy FX3U extension bus standard, allowing older analog or communication modules to operate.

Q: Can I communicate natively via EtherNet/IP from an iQ-R CPU's onboard network port?

Yes. Recent firmware versions on iQ-R CPU modules (such as the R04CPU or R16CPU) support native EtherNet/IP client/server communication functions directly through the integrated RJ45 network port. This eliminates the need for a dedicated RJ71EN71 network card in many basic third-party device integrations.

Q: How do I resolve a 'Power Supply Capacity Exceeded' error on an RQ expansion rack?

This occurs when the combined 5V DC power consumption of the installed Q-series modules surpasses the maximum output capacity of the extension base’s power supply (e.g., Q61P). To resolve this, recalculate the module currents and replace the power supply with a high-capacity unit like the Q64PN, or divide the modules across multiple RQ-type extension racks.