NXP Semiconductors MC68HC705C8AFNE

Overview

MC68HC705C8AFNE from Freescale Semiconductor is an 8-bit OTP microcontroller featuring 8 KB on-chip EPROM/OTPROM, 256 bytes 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 and legacy automotive subsystems.

For engineers reviewing the MC68HC705C8AFNE datasheet, MC68HC705C8AFNE pinout, MC68HC705C8AFNE application, or MC68HC705C8AFNE equivalent, key selection criteria include OTP memory size, dual serial interface support (SCI + SPI), 40-pin PDIP package compatibility, and COP watchdog configurability for safety-critical timing supervision.

Technical Context

The MC68HC705C8AFNE implements the M68HC05 CPU core with accumulator-based architecture, supporting 59 instructions and multiple addressing modes including indexed and relative. Its memory map integrates 8 KB OTPROM starting at $E000, 256-byte RAM from $0000–$00FF, and dedicated I/O register space.

It features two independent serial peripherals: an asynchronous SCI with programmable baud rate and full-duplex operation, and a synchronous SPI supporting master/slave modes with configurable clock polarity and phase. The 16-bit timer provides input capture for event timing and output compare for waveform generation.

Key Specifications

Pinout & Package

MC68HC705C8AFNE is packaged in a 40-pin plastic dual in-line package (PDIP) per Motorola case outline #824A, with 0.6-inch body width and 0.1-inch lead pitch. Pin 1 is marked by notch or dot; pin numbering follows standard DIP convention (counterclockwise from notch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705P6ACPE and MC68HC705B16CFNE, the MC68HC705C8AFNE uniquely balances 8 KB OTP, dual serial interfaces (SCI+SPI), and 40-pin PDIP compatibility-making it optimal for mid-complexity industrial controllers where CAN is unnecessary but SPI peripheral expansion is critical.

Availability

MC68HC705C8AFNE is available at Aetrix Electronics and suitable for industrial sensor nodes, legacy automotive subsystems, and appliance motor controllers requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705C8AFNE 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, headquartered in Austin, Texas.

The MC68HC705C8AFNE belongs to the M68HC05 family of 8-bit microcontrollers engineered for cost-sensitive, low-power embedded control applications in automotive, industrial, and consumer systems.

FAQ

What is the maximum operating frequency of the MC68HC705C8AFNE?

The MC68HC705C8AFNE supports a maximum internal bus frequency of 4 MHz, derived from an external crystal or resonator connected to OSC1/OSC2 pins. This corresponds to a 4 MHz instruction cycle rate for most operations, with timing validated across the full –40°C to +85°C industrial temperature range per its electrical specifications.

Does the MC68HC705C8AFNE support in-circuit programming?

No, the MC68HC705C8AFNE uses one-time programmable (OTP) EPROM and does not support in-circuit reprogramming. Programming requires a dedicated PROM programmer applying 12.5 V to the VPP pin (Pin 1) during write cycles. Once programmed and secured, code cannot be erased or rewritten.

Can the MC68HC705C8AFNE operate from a 3.3 V supply?

No, the MC68HC705C8AFNE is specified only for 5.0 V ±10% operation. Its DC electrical characteristics, timing parameters, and internal regulator are designed exclusively for 5 V. Using 3.3 V will result in undefined behavior, failed resets, or inability to execute instructions reliably.

What are the key differences between MC68HC705C8AFNE and MC68HSC705C8A?

The MC68HSC705C8A is a high-speed variant with identical pinout and OTP size but rated for up to 8 MHz bus frequency and tighter 3.3 V/5 V timing specs. The MC68HC705C8AFNE is the standard-speed version limited to 4 MHz and qualified only for 5 V operation per its Rev. 3 datasheet.

How is the COP watchdog configured on the MC68HC705C8AFNE?

The MC68HC705C8AFNE offers both programmable and non-programmable COP modes controlled via Option Register bits. In programmable mode, COP timeout is set using COPRST and COPCR registers (1.6 ms to 1.0 s); in non-programmable mode, timeout is fixed at ~16 ms. Both modes require periodic service writes to prevent reset.