NXP Semiconductors MC68HC000CRC8

Overview

MC68HC000CRC8 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 user/supervisor privilege modes, and targets embedded control systems requiring deterministic real-time interrupt response and memory-mapped I/O.

For engineers reviewing the MC68HC000CRC8 datasheet, MC68HC000CRC8 pinout, MC68HC000CRC8 application, or MC68HC000CRC8 equivalent, key selection criteria include bus timing compatibility with legacy 8/16-bit peripherals, DC/AC electrical specifications at 5 V ±10%, thermal derating above 70°C ambient, and support for asynchronous bus cycles using DTACK, BERR, and HALT signals.

Technical Context

The MC68HC000CRC8 uses a three-stage pipeline (fetch, decode, execute) and executes instructions in 1–56 clock cycles depending on addressing mode and operand size. It features a 16-bit external data bus with multiplexed address/data lines (A1–A23, D0–D15), supports both synchronous and fully asynchronous operation via DTACK handshake, and includes dedicated bus arbitration signals (BR, BG, BGACK).

Its exception handling architecture provides 256 vector locations, prioritized interrupt levels (seven autovector levels plus two spurious/uninitialized vectors), and supervisor/user stack frames with status register preservation. The processor requires external memory management and does not integrate cache or MMU.

Key Specifications

Pinout & Package

MC68HC000CRC8 is housed in a 68-lead ceramic quad flat pack (CQFP), case 746-01 (LC suffix), with 0.65 mm lead pitch and 27.94 mm × 27.94 mm body size. Pin numbering follows standard counter-clockwise orientation starting from top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC000CRC8, the MC68000P10 offers higher speed but demands more power and board space, while the MC68EC000RC20 enables modern 3.3 V system integration at the cost of architectural divergence and no drop-in replacement capability.

Availability

MC68HC000CRC8 is available at Aetrix Electronics and suitable for industrial automation, legacy test equipment, and medical diagnostics requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC000CRC8 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) pioneered the M68000 family, establishing industry-standard 16/32-bit architecture for embedded computing in the 1980s.

The MC68HC000 belongs to the CMOS-enhanced M68000 microprocessor line, designed specifically for low-power, high-reliability embedded systems where compatibility with existing M68000 software and hardware was essential.

FAQ

What is the maximum operating frequency of the MC68HC000CRC8?

The MC68HC000CRC8 is rated for a maximum clock frequency of 8 MHz under specified conditions (5 V ±10%, 0°C to +70°C). This limit is defined by AC timing parameters including setup/hold times for address and data signals, and cannot be exceeded without violating guaranteed timing margins. The MC68HC000CRC8 achieves this using a CMOS process that reduces dynamic power versus earlier HMOS versions.

Does the MC68HC000CRC8 support 32-bit data operations?

The MC68HC000CRC8 has a 32-bit internal architecture supporting 32-bit registers and instructions (e.g., MOVE.L, ADD.L), but its external data bus is strictly 16-bit (D0–D15). Therefore, 32-bit memory transfers require two consecutive bus cycles. The MC68HC000CRC8 does not support 32-bit external data transfers - that capability was introduced later with the MC68020.

Is the MC68HC000CRC8 pin-compatible with the original MC68000?

No, the MC68HC000CRC8 is not pin-compatible with the standard MC68000. While both use 68-pin packages, the MC68HC000CRC8 employs a ceramic quad flat pack (CQFP) with different pin assignments - notably, it lacks the VMA (Valid Memory Address) signal present on the MC68000 and reassigns several control lines. Board-level substitution requires schematic and layout revision.

What voltage levels are required for MC68HC000CRC8 operation?

The MC68HC000CRC8 requires a single 5 V ±10% supply (4.5 V to 5.5 V) applied to all V_CC pins. It is not 3.3 V tolerant, and applying voltages outside this range may cause functional failure or permanent damage. Decoupling capacitors (0.1 µF ceramic per V_CC pin) are mandatory to suppress switching noise on the CMOS core.

How does the MC68HC000CRC8 handle bus errors?

When the MC68HC000CRC8 samples BERR low during a bus cycle, it terminates the current access, pushes the program counter and status register onto the supervisor stack, and vectors to exception #2 (bus error). The MC68HC000CRC8 does not auto-retry the cycle - error recovery must be implemented in firmware by examining the saved address and status, then branching to appropriate handler code.