NXP Semiconductors MC68HC705C8ACFN

Overview

MC68HC705C8ACFN from Freescale Semiconductor is an 8-bit OTP-based microcontroller featuring 8 KB of on-chip EPROM/OTPROM, 192 bytes of RAM, a 16-bit capture/compare timer, SCI and SPI serial interfaces, and four 8-bit parallel I/O ports (PA–PD). It operates at up to 4 MHz internal bus speed with 5 V supply and supports low-power stop/wait modes. It targets embedded control in industrial sensors, motor controllers, and appliance subsystems.

For engineers reviewing the MC68HC705C8ACFN datasheet, MC68HC705C8ACFN pinout, MC68HC705C8ACFN application, or MC68HC705C8ACFN equivalent, key selection factors include OTP program retention, integrated timer for PWM generation, dual serial interface support (SCI + SPI), and compatibility with legacy M68HC05 toolchains and development hardware.

Technical Context

The MC68HC705C8ACFN implements the M68HC05 CPU core with accumulator- and index-register architecture, supporting 59 instructions and multiple addressing modes including inherent, immediate, direct, extended, and indexed variants. Its memory map allocates fixed locations for I/O registers, RAM, and PROM, with boot ROM enabling in-circuit programming via the SCI interface.

It integrates a programmable COP watchdog with both programmable and non-programmable reset options, clock monitor circuitry for oscillator failure detection, and configurable port logic - including bidirectional I/O on PA–PC and input-only PD pins. The timer module supports input capture for event timing and output compare for waveform generation.

Key Specifications

Pinout & Package

MC68HC705C8ACFN is packaged in a 44-pin QFP (Case #824A), with 40 usable I/O and power/control signals across four ports plus dedicated oscillator, reset, interrupt, and programming pins.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705C8ACFN, the P6A offers reduced memory and interface count for cost-sensitive designs, while the B16 adds ADC and doubles PROM capacity - making it preferable for mixed-signal applications where sensor digitization occurs on-board.

Availability

MC68HC705C8ACFN is available at Aetrix Electronics and suitable for industrial automation, appliance control, and legacy automotive subsystems requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705C8ACFN 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 architectures.

The MC68HC705C8ACFN belongs to the M68HC05 family - a line of cost-optimized, OTP-based microcontrollers targeting resource-constrained industrial and consumer control applications with minimal external components.

FAQ

What is the maximum operating frequency of the MC68HC705C8ACFN?

The MC68HC705C8ACFN supports a maximum internal bus frequency of 4 MHz, derived from an external crystal or resonator connected to OSC1/OSC2. This corresponds to a 4 MHz E-clock, which governs instruction execution timing, timer increments, and serial interface baud rates. The device is rated for operation across the full industrial temperature range (–40°C to +85°C) at this speed with 5.0 V ±10% supply.

Does the MC68HC705C8ACFN support in-system programming?

Yes, the MC68HC705C8ACFN supports in-system programming via its built-in SCI interface using the 256-byte bootloader ROM. Programming requires applying 12.5 V to the VPP pin and using Freescale's standard PROM programming protocol over SCI at predefined baud rates. No external programmer is needed, though proper voltage sequencing and timing per Section 9.3 must be observed.

How many I/O pins does the MC68HC705C8ACFN provide, and what are their configurations?

The MC68HC705C8ACFN provides 32 general-purpose I/O lines: PA0–PA7, PB0–PB7, PC0–PC7 (with multiplexed SCI/SPI functions), and PD0, PD5–PD7 (input-only). Port D pin PD6 is not connected, and PD1–PD4 are reserved. Each bidirectional port uses a data register and direction register (DDRA–DDRC); PD is read-only. Pull-ups on PA–PC are software-enabled via the OPTION register.

What low-power modes are available on the MC68HC705C8ACFN, and how do they differ?

The MC68HC705C8ACFN supports Run, Wait, Stop, and Data-Retention modes. Wait halts the CPU but keeps clocks active for peripherals; Stop disables the oscillator and most logic, retaining RAM and register contents with <10 µA typical current; Data-Retention maintains only RAM and COP logic at ~1 µA. All modes support wake-up via IRQ, timer events, or SCI activity - critical for battery-operated endpoints.

Is the MC68HC705C8ACFN pin-compatible with other members of the M68HC705 family?

No, the MC68HC705C8ACFN is not fully pin-compatible with other M68HC705 variants due to differences in port mapping, peripheral assignment, and package options. For example, the MC68HC705P6ACFN uses a 28-pin SOIC with fewer I/O and no SPI, while the MC68HC705B16CFN shares the 44-pin QFP but assigns different functions to several PC and PD pins. PCB layout must be verified against each specific device's pin assignment diagrams (Figures 1-3 to 1-6).