Mitsubishi MELSEC-A Series Modules AJ71PT32-S3

Technical Dossier

Product Details And Specifications

Mitsubishi Electric MELSEC-A Series Technical Notes

Q: How are RFQ terms confirmed?
A: Quantity, required condition, documentation needs, destination and sourcing route are confirmed during RFQ review before quotation.

The Evolution of MELSEC-A Series Architecture

The MELSEC-A Series was introduced in the early 1980s as a successor to Mitsubishi's MELSEC-K platform. The architecture is built around a parallel backplane bus (A-BUS) that supports synchronous data exchange between CPU modules and peripheral I/O, communication, and special function modules. Early configurations centered on the A2CPU and A3CPU processors, which used proprietary ladder logic execution engines with fixed scan cycles. By the late 1980s, Mitsubishi introduced the A2ACPU and A3ACPU variants with expanded program memory and enhanced interrupt handling for high-speed process control.

The 1990s saw the integration of open fieldbus protocols into the MELSEC-A ecosystem. The AJ71PT32-S3 PROFIBUS-DP master module and the AJ71PB92D represent this generation — purpose-built communication adapters that bridged the proprietary A-BUS to IEC 61158-compliant fieldbus networks. This allowed MELSEC-A systems to interface with third-party field devices (valve positioners, variable frequency drives, remote I/O stations) without replacing the core CPU infrastructure. Compatibility constraints are significant: these communication modules are slot-position dependent, require specific base unit types (A38B, A68B, A98B), and are not forward-compatible with the MELSEC-Q or MELSEC-iQ-R platforms without gateway hardware.

The MELSEC-A Series entered end-of-life (EOL) status progressively between 2008 and 2015. Mitsubishi Electric officially discontinued manufacturing of most A-Series modules by 2013, with the recommended migration path being the MELSEC-Q Series (QnUDE CPU family) or the current MELSEC iQ-R platform. However, due to the capital cost of full system replacement and the complexity of re-engineering validated process control logic, a substantial installed base remains in active service globally, particularly in the chemical processing and power generation sectors.

MELSEC-A Series Full Catalog & Functionalities (SKU List)

CPU Modules

• A2CPU-S1: Standard CPU, 8K step program memory, basic ladder execution
• A3CPU: High-performance CPU, 30K step memory, extended I/O addressing
• A2ACPU: Advanced CPU with 14K steps, enhanced interrupt and index register support
• A3ACPU: High-capacity advanced CPU, 30K steps, dual-port RAM for HMI access
• A2UCPU: Universal CPU with MELSECNET/10 compatibility, 28K steps
• A3UCPU: High-speed universal CPU, 60K steps, multi-program execution

Digital Input (DI) Modules

• AX40: 16-point DC input module, 24VDC sink/source, 10ms response
• AX80: 32-point DC input module, 24VDC, high-density I/O configuration
• AX10: 8-point AC input module, 100–120VAC, isolated commons

Digital Output (DO) Modules

• AY40: 16-point transistor output, 24VDC, 0.5A per point, sink type
• AY80: 32-point transistor output, 24VDC, high-density configuration
• AY10: 8-point relay output module, 240VAC/2A per point

Analog I/O Modules

• A68AD: 8-channel analog input, 12-bit resolution, 4–20mA / 0–10V selectable
• A62DA: 2-channel analog output, 12-bit, 4–20mA / 0–10V

Communication & Network Modules

• AJ71PT32-S3: PROFIBUS-DP master module, max 125 slave stations, 12Mbps, A-BUS interface — the subject SKU of this page
• AJ71PB92D: PROFIBUS-DP slave module, for integration into upstream PROFIBUS master networks
• AJ71E71: Ethernet interface module, 10BASE-T, TCP/IP and UDP/IP support
• AJ71QLP21: MELSECNET/10 optical loop master/local module
• AJ71QBR11: MELSECNET/10 coaxial bus master/local module

Power Supply Modules

• A61P: 5VDC/6A power supply for A-Series base units, 100–240VAC input
• A62P: 5VDC/8A power supply, extended capacity for fully populated base units

Sourcing Hard-to-Find & Obsolete MELSEC-A Series Parts

Q: Can you support multi-unit or repeat RFQ requests?
A: Yes. Send the model list, target quantity and destination so DRIVEKNMS can review sourcing options and quote the requirement as a project RFQ.