NXP Semiconductors MC68020EH33E

Overview

MC68020EH33E from Freescale Semiconductor (formerly Motorola) is a 32-bit, second-generation enhanced microprocessor with full 32-bit data and address buses (A31–A0, D31–D0), on-chip 256-byte instruction cache, pipelined architecture, and support for coprocessor interface (CP0–CP3). It operates at 33 MHz maximum clock frequency, supports supervisor/user privilege levels, and implements full virtual memory management via MMU-compatible bus protocol - used in high-end embedded workstations, industrial controllers, and early UNIX-based systems.

For engineers reviewing the MC68020EH33E datasheet, MC68020EH33E pinout, MC68020EH33E application, or MC68020EH33E equivalent, key selection criteria include its 33 MHz max CPU clock, 32-bit synchronous/asynchronous bus interface, coprocessor handshake protocol (FC2–FC0, AS, DTACK), exception vectoring model, and compatibility with M68000-family toolchains and operating systems such as VxWorks, pSOS, and early Linux ports.

Technical Context

The MC68020EH33E implements a five-stage pipeline (fetch, decode, execute, memory access, write-back) with dynamic bus sizing (8/16/32-bit transfers), misaligned operand handling, and asynchronous bus timing controlled by DTACK, DSACK0/DSACK1, and BERR signals. Its coprocessor interface uses dedicated CIR registers (Control, Response, Save, Restore) and 19 defined response primitives including Busy, Null, Transfer Effective Address, and Exception primitives.

It features a Harvard-style on-chip instruction cache (256 bytes, 4-way set associative), cache control register (CACR), and cache address register (CAAR); supports up to 4 GB linear address space; and provides 256 exception vectors mapped to fixed locations in low memory - enabling deterministic real-time interrupt latency and precise bus fault recovery via Special Status Word (SSW) and stack frame formats.

Key Specifications

Pinout & Package

MC68020EH33E is housed in a 132-pin ceramic PGA (Pin Grid Array) package with 1.27 mm pitch, compliant with JEDEC MO-058. Pin assignments follow Motorola standard layout for RC/RP suffix devices, with dedicated power/ground pins distributed across all four sides for noise reduction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 32-bit embedded microprocessor applications.

Compared with MC68020EH33E, MC68030RC33 adds integrated MMU and data cache at higher power and pin-function complexity, while MC68EC020FN33 sacrifices address space and bus flexibility for smaller footprint and lower cost - making the MC68020EH33E optimal for balanced performance, expandability, and legacy system compatibility.

Availability

MC68020EH33E is available at Aetrix Electronics and suitable for industrial motion controllers, legacy UNIX workstations, avionics display processors, and medical imaging acquisition nodes requiring stable component supply and long-term obsolescence management.

Supply support for MC68020EH33E 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

Freescale Semiconductor (acquired from Motorola in 2004) is a fabless semiconductor company specializing in embedded processing, analog, and connectivity solutions for automotive, industrial, and networking markets.

The MC68020 product line was designed as a high-performance 32-bit upgrade path from the M68000 family, targeting real-time embedded systems requiring deterministic interrupt response, virtual memory support, and coprocessor extensibility - not general-purpose computing.

FAQ

What is the maximum operating frequency of the MC68020EH33E?

The MC68020EH33E is rated for a maximum clock frequency of 33 MHz, as confirmed by Motorola's Electrical Characteristics specification (Section 10.3, AC Electrical Characteristics). This frequency defines the upper limit for stable instruction execution, bus timing, and coprocessor handshake synchronization. Exceeding 33 MHz may result in undefined behavior, pipeline stalls, or bus protocol violations. The 'H33' suffix in MC68020EH33E explicitly denotes this speed grade.

Does the MC68020EH33E include an integrated memory management unit (MMU)?

No, the MC68020EH33E does not include an integrated MMU. It provides the bus protocol and exception vectors necessary for external MMU implementation (e.g., using the MC68851), but contains no on-die translation lookaside buffer (TLB) or page table walker. Unlike the later MC68030, the MC68020EH33E relies on external logic for virtual-to-physical address translation - a key distinction documented in Section 1.5 (Virtual Memory) and Section 5 (Bus Operation) of the M68020 User's Manual.

What package type and pin count does the MC68020EH33E use?

The MC68020EH33E uses a 132-pin ceramic Pin Grid Array (PGA) package with 1.27 mm pitch, as specified in Section 11.2.1 (MC68020 RC and RP Suffix - Pin Assignment) of the M68020 User's Manual. This package is mechanically and electrically compatible with other RC/RP-suffix MC68020 variants and supports full signal routing for 32-bit data/address buses, coprocessor interface, and asynchronous bus control - distinguishing it from the 84-pin PQFP used by the MC68EC020 series.

How does the MC68020EH33E handle misaligned memory accesses?

The MC68020EH33E handles misaligned 16-bit and 32-bit memory accesses in hardware without generating exceptions, unlike earlier M68000-family parts. When a misaligned operand is encountered (e.g., loading a 32-bit word from address 0x1001), the processor automatically performs multiple aligned transfers and combines results - transparently to software. This capability is explicitly documented in Section 5.2.2 (Misaligned Operands) and reduces porting effort for C-based applications compiled without strict alignment enforcement.

What is the role of the FC2–FC0 signals on the MC68020EH33E?

The FC2–FC0 (Function Code) signals on the MC68020EH33E are three output lines that encode the type and purpose of the current bus cycle - such as data read, data write, instruction fetch, or CPU-space access. These signals drive external memory mapping logic and peripheral decoders, enabling cycle-specific address decoding without additional glue logic. Their encoding is defined in Section 3.2 of the M68020 User's Manual and remains active throughout the bus cycle, synchronized with AS and DTACK.