NXP Semiconductors MC68HC000RC8

Overview

MC68HC000RC8 from Motorola (now NXP/Freescale) is a CMOS 16/32-bit microprocessor with 32-bit internal architecture, 24-bit address bus (16 MB), 16-bit data bus, and 8 MHz maximum clock frequency. It implements the full M68000 instruction set, supports supervisor/user privilege modes, and targets embedded control systems requiring deterministic real-time interrupt response and memory-mapped I/O.

For engineers reviewing the MC68HC000RC8 datasheet, MC68HC000RC8 pinout, MC68HC000RC8 application, or MC68HC000RC8 equivalent, key selection criteria include bus timing compatibility with legacy M68K peripherals, DC/AC electrical specifications at 8 MHz operation, thermal derating in plastic DIP packages, and exception vector mapping for real-time OS integration.

Technical Context

The MC68HC000RC8 uses a three-stage pipeline (fetch-decode-execute) and executes instructions in 1–5 clock cycles depending on addressing mode and operand size. It features a 16-bit external data bus with multiplexed address/data lines, asynchronous bus control via DTACK, BERR, and HALT signals, and supports both 8-bit and 16-bit memory and I/O transfers.

Its exception handling includes 256 vectored interrupts, seven priority levels, bus error recovery, and supervisor/user stack separation. The processor implements full M68000 binary compatibility while reducing power consumption via CMOS technology versus the original NMOS MC68000.

Key Specifications

Pinout & Package

MC68HC000RC8 is housed in a 64-pin ceramic dual in-line package (Case 765A-05, RC suffix), with 0.3-inch body width and 0.1-inch pin pitch. Pin assignments follow the standard MC68000 pinout layout with dedicated address, data, control, and power terminals.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16/32-bit microprocessor applications.

Compared with MC68HC000RC8, the MC68000P8 offers broader temperature tolerance but higher thermal load, while the MC68EC000RC8 reduces feature set and cost at the expense of full instruction set compatibility-making the MC68HC000RC8 optimal for legacy-replacement designs needing CMOS efficiency and complete M68K software support.

Availability

MC68HC000RC8 is available at Aetrix Electronics and suitable for industrial PLC controllers, legacy test equipment, medical diagnostic instruments, and avionics data recorders requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC000RC8 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 via Freescale acquisition) pioneered the M68000 family and established industry standards for 16/32-bit CISC microprocessors in the 1980s.

The MC68HC000RC8 belongs to the M68000 microprocessor product line, designed specifically for embedded control applications requiring high instruction density, deterministic interrupt response, and backward compatibility with NMOS predecessors.

FAQ

What is the maximum operating frequency of the MC68HC000RC8?

The MC68HC000RC8 is rated for a maximum clock frequency of 8 MHz under specified DC and AC conditions. This limit is defined by internal propagation delays and setup/hold timing requirements for address, data, and control signals. Operation above 8 MHz may result in undefined behavior or timing violations, particularly in asynchronous bus cycles where DTACK assertion timing becomes critical. The MC68HC000RC8 datasheet specifies all AC parameters-including clock high/low times, read/write pulse widths, and bus arbitration intervals-at this 8 MHz rating.

Does the MC68HC000RC8 support the full M68000 instruction set?

Yes, the MC68HC000RC8 implements the complete M68000 instruction set architecture, including all addressing modes, privilege-level instructions (e.g., MOVE from SR), and exception-handling opcodes. It maintains binary compatibility with software written for the original NMOS MC68000, enabling direct firmware reuse. Differences are limited to implementation details-such as CMOS power characteristics and minor timing variations-not functional instruction set omissions. The MC68HC000RC8 User's Manual explicitly confirms full ISA compliance in Section 1.4.

What package type does the MC68HC000RC8 use?

The MC68HC000RC8 uses a 64-pin ceramic dual in-line package (DIP) designated Case 765A-05, identified by the "RC" suffix in the part number. This package features a 0.3-inch body width, 0.1-inch pin pitch, and through-hole mounting compatible with legacy PCB layouts. Unlike plastic DIP variants, the ceramic construction provides superior thermal stability and hermetic sealing, supporting reliable operation in industrial environments where moisture or thermal cycling could affect plastic encapsulants.

How does the MC68HC000RC8 handle bus errors?

The MC68HC000RC8 asserts the BERR signal during an invalid memory or I/O access, then automatically vectors to exception vector #2 (bus error) after completing the current instruction. The processor saves the program counter and status register onto the supervisor stack and begins executing the bus error handler. Unlike the MC68010, the MC68HC000RC8 does not implement delayed bus error reporting-it responds synchronously with the faulting cycle. Recovery depends entirely on firmware handling; no automatic retry or correction is performed in hardware.

Is the MC68HC000RC8 pin-compatible with other M68000 family members?

The MC68HC000RC8 shares identical pinout and signal definitions with the MC68000P8 and MC68EC000RC8 in the 64-pin DIP package, making it mechanically and electrically interchangeable on boards designed for that footprint. However, functional differences exist: the MC68EC000RC8 omits certain privileged instructions, and the NMOS MC68000P8 draws significantly more current. Voltage levels, timing margins, and drive strength are compatible, but thermal design must account for the MC68HC000RC8's lower power dissipation.