NXP Semiconductors MC68EC020AA25R

Overview

MC68EC020AA25R from Motorola is a 32-bit embedded microprocessor with 25 MHz maximum clock frequency, 256-byte instruction cache, and 24-bit address bus (A23–A0) supporting up to 16 MB physical memory. It implements the full MC68000 family instruction set, features pipelined execution, supervisor/user privilege levels, and on-chip bus arbitration logic - deployed in industrial controllers and legacy telecom terminal equipment.

For engineers reviewing the MC68EC020AA25R datasheet, MC68EC020AA25R pinout, MC68EC020AA25R application, or MC68EC020AA25R equivalent, key selection considerations include its embedded-optimized feature set (no MMU, reduced address bus), 25 MHz timing compliance, RP package thermal profile, and compatibility with MC68000-family toolchains and peripheral interfaces.

Technical Context

The MC68EC020AA25R implements a three-stage pipeline (fetch, decode, execute) with dynamic bus sizing support for 8-/16-/32-bit data transfers and misaligned operand handling. Its on-chip 256-byte instruction cache operates in write-through mode and is invalidated on reset or via software control using the Cache Control Register (CACR).

It supports asynchronous bus cycles with DSACK0/DSACK1 handshake signals, three-wire bus arbitration (BR, BG, BGACK), and exception processing via 256-vector table. Unlike the MC68020, it omits the full 32-bit address bus (A31–A0), coprocessor interface pins (CPA0–CPA2), and MMU - confirming its embedded-system targeting.

Key Specifications

Pinout & Package

MC68EC020AA25R is housed in a 84-pin ceramic Pin Grid Array (PGA) package with RP suffix, designed for high-reliability industrial environments and compatible with standard PGA sockets. Thermal resistance (θ_JA) is 35°C/W under JEDEC JESD51-2 conditions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar embedded microprocessor applications.

Compared with MC68EC020AA25R, the RC25 variant trades industrial-grade packaging for lower cost, while the MC68332ACPV16 replaces external bus scalability with integrated peripherals - making AA25R optimal for memory-expandable, thermally demanding embedded hosts.

Availability

MC68EC020AA25R is available at Aetrix Electronics and suitable for industrial PLC controllers, legacy telecom terminals, medical diagnostic instruments, and avionics data concentrators requiring stable component supply and long-term obsolescence management.

Supply support for MC68EC020AA25R includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Motorola Semiconductor (now part of NXP Semiconductors) was a pioneer in 32-bit microprocessor architecture, delivering high-reliability silicon for automotive, industrial, and communications markets from the 1970s through early 2000s.

The MC68EC020 product line was engineered as a cost- and power-optimized derivative of the MC68020, removing the MMU and full 32-bit address bus to serve deterministic embedded control applications with predictable timing and simplified board design.

FAQ

What is the maximum operating frequency of the MC68EC020AA25R?

The MC68EC020AA25R is rated for a maximum clock frequency of 25 MHz, as confirmed by Motorola's Electrical Characteristics specification (Section 10.3, AC Electrical Characteristics). This frequency defines the upper limit for reliable instruction execution, bus cycle timing, and peripheral interface synchronization. Operating above 25 MHz may result in undefined behavior or timing violations. The '25' in the part number explicitly denotes this speed grade.

Does the MC68EC020AA25R include an MMU or floating-point unit?

No, the MC68EC020AA25R does not include a Memory Management Unit (MMU) or integrated floating-point unit (FPU). As documented in the M68020 User's Manual Preface and Section 1.1, the MC68EC020 is an embedded variant that omits the MMU and coprocessor interface pins present on the full MC68020. Floating-point operations require an external MC68881 or MC68882 FPU connected via the coprocessor interface - which the MC68EC020AA25R does not support.

What package type and pin count does the MC68EC020AA25R use?

The MC68EC020AA25R uses an 84-pin ceramic Pin Grid Array (PGA) package with RP suffix, as specified in Section 11.2.7 and 11.2.8 of the M68020 User's Manual. This package provides enhanced thermal performance (θ_JA = 35°C/W) and mechanical robustness for industrial environments. It is socket-compatible with standard 84-pin PGA sockets and distinct from the plastic RC package used in commercial-grade variants.

How does the MC68EC020AA25R handle bus arbitration?

The MC68EC020AA25R implements a dedicated three-wire bus arbitration protocol using BR (Bus Request), BG (Bus Grant), and BGACK (Bus Grant Acknowledge) signals, detailed in Section 5.7.2 of the User's Manual. This hardware-managed arbitration allows the processor to yield the bus to DMA controllers without software intervention, enabling concurrent data movement and CPU execution - a key requirement for real-time embedded systems with high-bandwidth peripherals.

Is the MC68EC020AA25R pin-compatible with the MC68020?

No, the MC68EC020AA25R is not pin-compatible with the MC68020. While both share the 84-pin PGA footprint, the MC68EC020AA25R repurposes or omits pins used for the full 32-bit address bus (A24–A31), coprocessor interface (CPA0–CPA2), and MMU control signals. Section 3.3 and Appendix A of the User's Manual explicitly confirm the MC68EC020's 24-bit address bus (A23–A0) and absence of coprocessor pins - requiring PCB redesign for migration from MC68020.