NXP Semiconductors MC68HC705C8AB

Overview

MC68HC705C8AB from Freescale Semiconductor is an 8-bit OTP microcontroller based on the M68HC05 core, featuring 8 KB of on-chip OTPROM, 256 bytes of RAM, a 16-bit capture/compare timer, SCI and SPI serial interfaces, and four 8-bit I/O ports (PA–PD). It operates at up to 4 MHz internal bus speed and supports 5 V operation in PDIP, PLCC, QFP, and SDIP packages for embedded control in industrial sensors and appliance subsystems.

For engineers reviewing the MC68HC705C8AB datasheet, MC68HC705C8AB pinout, MC68HC705C8AB application, or MC68HC705C8AB equivalent, key selection criteria include OTPROM capacity, dual serial interface support (SCI + SPI), low-power stop/wait modes with COP watchdog, and compatibility with legacy M68HC05 toolchains and development hardware.

Technical Context

The MC68HC705C8AB implements the M68HC05 CPU core with 40+ instructions, indexed and relative addressing, and a 16-bit program counter. Its memory architecture includes 8 KB OTPROM mapped into a 16 KB address space, 256-byte RAM, and dedicated bootloader ROM for in-system programming via SCI.

Peripheral integration includes a 16-bit timer with input capture and output compare functions, full-duplex asynchronous SCI supporting baud rates up to 19.2 kbps at 4 MHz, and synchronous SPI master/slave mode with programmable clock polarity and phase - all accessible through memory-mapped I/O registers and interrupt-driven operation.

Key Specifications

Pinout & Package

The MC68HC705C8AB is available in multiple packages including 40-pin PDIP, 44-pin PLCC, 44-pin QFP, and 42-pin SDIP. The 'B' suffix denotes the QFP variant per Freescale ordering conventions (e.g., MC68HC705C8AB = 44-pin QFP).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705P6ACD, the MC68HC705C8AB adds SPI, SCI, and full 16-bit timer functionality - enabling richer communication and timing capabilities without changing package or power requirements. Against MC68HC705B16CD, it trades 8 KB less OTPROM for identical peripheral integration and lower unit cost in volume production.

Availability

MC68HC705C8AB is available at Aetrix Electronics and suitable for industrial sensor nodes, home appliance control systems, and legacy automotive subsystems requiring stable component supply and long-lifecycle support.

Supply support for MC68HC705C8AB 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 (now part of NXP Semiconductors) was a leading designer of embedded processors and analog/mixed-signal ICs, known for the 68K and ColdFire families.

The MC68HC705C8AB belongs to the M68HC05 microcontroller family, designed for cost-sensitive, low-power 8-bit control applications in automotive, industrial, and consumer electronics where OTP security and peripheral integration were critical.

FAQ

What is the maximum operating frequency of the MC68HC705C8AB?

The MC68HC705C8AB supports a maximum internal bus frequency of 4 MHz, corresponding to a 4 MHz crystal or resonator on OSC1/OSC2. At this speed, instruction execution times range from 0.5 µs (shortest) to 4 µs (longest), enabling responsive real-time control in applications such as motor sequencing and sensor sampling. The MC68HC705C8AB does not support external clock sources above 4 MHz.

Does the MC68HC705C8AB support in-system programming (ISP)?

Yes, the MC68HC705C8AB supports in-system programming via its Serial Communications Interface (SCI). Using the built-in bootloader ROM, firmware can be loaded into RAM and executed or programmed into OTPROM using standard Freescale programming routines. This capability eliminates the need for external programmers during development and field updates, though OTPROM can only be programmed once per location.

What are the power supply requirements for the MC68HC705C8AB?

The MC68HC705C8AB operates from a single 5.0 V ±10% supply (VDD), with VSS as ground reference. It is not rated for 3.3 V operation - Freescale specifies separate 3.3 V variants (e.g., MC68HC705C8ACF) with different electrical characteristics. Decoupling requires a 0.1 µF ceramic capacitor placed close to the VDD pin, per Freescale's layout recommendations in the datasheet.

How many I/O pins does the MC68HC705C8AB provide, and what is their configuration?

The MC68HC705C8AB provides 32 general-purpose I/O lines across four 8-bit ports (PA–PD), with Port D offering 7 usable pins (PD0–PD5 and PD7; PD6 is not bonded). Each port features individual data direction control via DDR registers, and Port B supports interrupt-on-change functionality. All ports are CMOS-compatible with TTL-level inputs and can sink/source up to 1.6 mA per pin under specified conditions.

Is the MC68HC705C8AB still in production, and what is its lifecycle status?

The MC68HC705C8AB was discontinued by Freescale (now NXP) in the mid-2000s as part of the migration to the S08 and Kinetis families. However, Aetrix Electronics maintains active inventory and offers extended lifecycle support, including traceable sourcing from authorized legacy distributors and engineering assistance for design-in and obsolescence mitigation of the MC68HC705C8AB in ongoing production programs.