The FX5-CNV-IF is a conversion adapter from Mitsubishi Electric that enables MELSEC FX3-series extension modules and special function modules to be connected to a MELSEC iQ-F FX5 series CPU. It bridges the physical and electrical interface differences between the two generations, preserving investment in existing FX3 peripheral hardware during system upgrades. The FX5-CNV-IF is available through Atlantech Drives — quote within 24–48 hours, worldwide express shipping, 12-month warranty.
What Is the Mitsubishi FX5-CNV-IF?
The FX5-CNV-IF is a passive interface conversion module that mounts on the right side of an FX5U or FX5UC CPU (or after any FX5 native extension module) and presents a standard FX3-series expansion connector on its right side, allowing the full range of FX3U and FX3UC extension blocks and special function modules to be appended to an FX5 system. Without this adapter, FX3-series modules cannot be physically or electrically connected to the FX5 expansion bus. The FX5-CNV-IF consumes no I/O points itself and does not require configuration in GX Works3 — it is transparent to the CPU, which simply addresses the downstream FX3 modules as if they were native FX5 extensions, subject to compatibility restrictions detailed below.
Key Technical Specifications
- Function: FX5 to FX3 expansion bus conversion
- Compatible FX5 CPUs: FX5U, FX5UC
- Compatible downstream modules: FX3U and FX3UC extension blocks and special function modules (see restrictions)
- I/O points consumed: 0 (transparent to CPU)
- Power supply: Supplied from FX5 CPU expansion bus
- Maximum extension modules after FX5-CNV-IF: Up to 8 FX3-series modules (subject to FX5 system I/O limit)
- Certifications: CE
- Operating temperature: 0 to 55°C
- Dimensions (W × H × D): 40 × 90 × 87 mm
Architecture & Design Overview
The FX5-CNV-IF solves a specific migration challenge: Mitsubishi redesigned the FX5 expansion bus with a higher-speed serial interface incompatible with the FX3’s parallel bus architecture. The FX5-CNV-IF contains a protocol bridge that translates between the two bus standards transparently, without introducing additional scan cycle overhead beyond the inherent latency of the FX3-series modules themselves. One FX5-CNV-IF is permitted per FX5 CPU — only a single conversion block is supported in the expansion chain. FX5 native modules (FX5-8EX, FX5-8EYT, etc.) must be placed between the CPU and the FX5-CNV-IF; FX3-series modules must be placed to the right of the adapter. Mixing FX5 native modules to the right of the FX5-CNV-IF is not supported. This architecture means the migration strategy is typically: CPU → FX5 native modules (new additions) → FX5-CNV-IF → existing FX3 modules (retained from previous system). Not all FX3U special function modules are compatible; modules requiring direct CPU bus access for high-speed data transfer (such as the FX3U-ENET and FX3U-USB-BD) cannot be used downstream of the FX5-CNV-IF — always consult the MELSEC iQ-F FX5U User’s Manual (Hardware) compatibility table before specifying FX3 modules for use with this adapter.
Expert Tips
- When planning an FX3U-to-FX5U migration, use the FX5-CNV-IF as a transitional measure to retain FX3 analog I/O modules (FX3U-4AD, FX3U-4DA) that would otherwise require replacement. This defers hardware cost while allowing the CPU and programming environment to be upgraded to GX Works3 immediately.
- After installing the FX5-CNV-IF and downstream FX3 modules, always perform a GX Works3 «Read from PLC» to auto-detect the system configuration and verify that all FX3 modules are correctly identified in the module list. Any unrecognised module downstream of the adapter indicates a compatibility issue, not a wiring fault.
- The FX5-CNV-IF does not support FX2N-series modules — only FX3U and FX3UC extension blocks and special function modules are compatible. FX2N modules have a different bus timing that the bridge cannot accommodate.
- If the FX5 system I/O count approaches the 512-point limit of the FX5U CPU, note that FX3-series modules connected via the FX5-CNV-IF count toward this total in the same way as native FX5 modules.
Frequently Asked Questions
Q: Can more than one FX5-CNV-IF be used in a single FX5 system?
A: No. Only one FX5-CNV-IF is permitted per FX5 CPU system. Cascading two adapters is not supported and will result in system errors.
Q: Is the FX5-CNV-IF compatible with the FX5UJ CPU?
A: No. The FX5-CNV-IF is compatible with FX5U and FX5UC only. The FX5UJ has a different expansion architecture with a more limited extension capability and does not support the FX5-CNV-IF.
Q: Can FX3U high-speed counter modules (FX3U-2HC) be used downstream of the FX5-CNV-IF?
A: This must be verified against the compatibility table in the FX5U Hardware Manual, as high-speed modules with dedicated bus access requirements are frequently excluded. As a general rule, standard I/O extension blocks and basic analog modules are reliably compatible; high-speed and network modules require individual verification.
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