Mitsubishi MELSEC AnS Series Modules: A2ASCPU

Technical Dossier

Product Details And Specifications

Mitsubishi MELSEC AnS Series: Comprehensive Module Range and Technical Overview

The Mitsubishi MELSEC AnS Series (also referred to as the A-Series Small Format) is a compact programmable logic controller platform engineered for discrete and process control applications in heavy industry. Deployed across chemical processing plants, petroleum refineries, nuclear utility facilities, and automotive assembly lines globally, the AnS Series established a benchmark for modular PLC architecture in the 1980s and 1990s. Its backplane-based I/O expansion, deterministic scan cycle, and compatibility with Mitsubishi's GX Developer and MELSEC MEDOC programming environments made it a standard specification in long-lifecycle industrial installations. Units remain operational in facilities where replacement of the entire control system is cost-prohibitive, making spare parts availability a critical operational requirement.

The Evolution of AnS Series Architecture

The MELSEC AnS Series emerged as a miniaturized derivative of Mitsubishi's full-size A Series (A2A, A3A, A3H), sharing the same instruction set and ladder logic programming model while reducing the physical footprint for panel-mount installations. The original AnS platform used a parallel backplane bus operating at TTL logic levels, with CPU modules executing relay ladder, function block, and structured text via the MELSEC instruction set.

Early-generation CPUs such as the A1SCPU and A2ASCPU supported program memory in the range of 8K to 30K steps, with battery-backed SRAM for program retention. Subsequent revisions introduced the A2ASCPU-S1 and A2USCPU variants, extending memory capacity and adding built-in RS-232C and RS-422 communication ports. The AnS Series was progressively superseded by the MELSEC Q Series (circa 2000) and later the iQ-R Series, both of which offer higher scan speeds, larger memory, and Ethernet-native communication. As of 2026, the entire AnS Series is classified as End-of-Life (EOL) by Mitsubishi Electric, with no new production. Compatibility bridging to Q Series is achievable via the A1S-QAS conversion adapter, though I/O module pinouts and base configurations require engineering review.

AnS Series Full Catalog & Functionalities (SKU List)

CPU Modules

• A2ASCPU: Standard CPU, 30K-step program memory, RS-232C port, AnS base compatible.
• A2ASCPU-S1: Enhanced CPU variant with extended I/O addressing and built-in data register expansion.
• A1SCPU: Entry-level CPU, 8K-step memory, single-slot base, suited for small standalone applications.
• A1SCPUC24-R2: CPU with integrated dual RS-232C/RS-422 communication channels.
• A2UCPU: High-performance CPU with 60K-step capacity and multi-program execution support.
• A2USCPU-S1: Extended A2UCPU with additional special function register support.
• A3UCPU: Top-tier AnS-compatible CPU, 120K-step memory, multi-task execution.

Digital Input (DI) Modules

• A1SX10: 16-point DC input module, 24VDC, sink/source compatible.
• A1SX30: 32-point DC input module, 24VDC, high-density terminal block.
• A1SX40: 16-point DC input, isolated commons, for high-noise environments.
• A1SX80: 16-point AC input module, 100–120VAC, for legacy AC field wiring.

Digital Output (DO) Modules

• A1SY10: 16-point relay output, 2A per point, for motor starter and solenoid control.
• A1SY40P: 16-point transistor output, 0.5A, source type, 24VDC load.
• A1SY80: 16-point triac output, 100–240VAC, for AC load switching.

Analog I/O Modules

• A1S62DA: 2-channel analog output, 12-bit resolution, 0–10V / 4–20mA selectable.
• A1S64AD: 4-channel analog input, 12-bit, voltage and current input modes.

Communication & Network Modules

• A1SJ71UC24-R2: Serial communication module, RS-232C/RS-422, MELSEC protocol support.
• A1SJ71QLP21: MELSECNET/10 optical loop network module for peer-to-peer PLC communication.
• A1SJ71E71-B2: Ethernet interface module, 10BASE-T, for SCADA and HMI connectivity.

Power Supply Modules

• A1S61PN: 5VDC/3A power supply for AnS slim base units.
• A1S62PN: Dual-output power supply, 5VDC/3A + 24VDC/0.6A, for mixed I/O configurations.

Sourcing Hard-to-Find & Obsolete AnS Series Parts

Quality Control for the AnS Series Range

AnS Series modules present specific test challenges due to their parallel backplane bus architecture and battery-dependent program retention. DriveKNMS applies the following verification protocol to all AnS Series stock:

• Backplane Bus Integrity Test: Each module is seated in a reference AnS base unit and scanned for address conflicts, bus contention, and signal timing deviations.
• CPU Program Retention Verification: SRAM-backed CPU modules (A2ASCPU, A1SCPU, A2UCPU) are loaded with a reference ladder program and cycled through a 72-hour power-off retention test to validate battery and SRAM condition.
• I/O Point Functional Test: All digital input and output modules are tested point-by-point at rated voltage and current. Analog modules are calibrated against a traceable reference standard.
• Communication Port Loopback Test: CPU modules with integrated RS-232C or RS-422 ports are verified using MELSEC protocol loopback at rated baud rates.
• Visual and Component Inspection: Capacitor condition, connector pin integrity, and PCB surface are inspected under magnification. Modules with evidence of thermal stress or corrosion are rejected.