NXP Semiconductors MC68HC705KJ1CP

Overview

MC68HC705KJ1CP from Freescale Semiconductor is a 8-bit HCMOS microcontroller in the M68HC05 family, featuring a 4.0-MHz internal operating frequency at 5.0 V, 1240 Bytes of EPROM/OTPROM, 64 Bytes of RAM, and integrated peripherals including a 15-stage multifunction timer and COP watchdog. It delivers robust noise immunity and supports keyboard scan with interrupt on four I/O pins for embedded control in industrial sensors and appliance interfaces.

For engineers reviewing the MC68HC705KJ1CP datasheet, MC68HC705KJ1CP pinout, MC68HC705KJ1CP application, or MC68HC705KJ1CP equivalent, key selection criteria include its 10 bidirectional I/O lines (with 10-mA sink and 5.5-mA source capability), fully static operation, selectable oscillator options (crystal, ceramic resonator, RC, or external clock), and support for stop/wait/data-retention low-power modes.

Technical Context

The MC68HC705KJ1CP implements the 68HC05 CPU core with accumulator, index register, stack pointer, and condition code register. Its instruction set includes inherent, immediate, direct, extended, and indexed addressing modes, supporting read-modify-write, bit manipulation, and control instructions for deterministic real-time control.

It integrates memory-mapped I/O registers, a 15-stage timer with real-time and overflow interrupts, and a configurable COP watchdog with timeout period determined by internal prescaler. The MCU supports edge- or level-sensitive external interrupt triggering via IRQ/VPP and provides software-programmable pulldowns on all I/O pins.

Key Specifications

Pinout & Package

MC68HC705KJ1CP is housed in a 16-pin plastic dual in-line package (PDIP), Case #648, with 0.3-inch body width and 0.1-inch lead pitch. Pin assignments are standardized across the KJ1 family and validated per Freescale Rev. 4.1 datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705KJ1CP, the MC68HC705P6CP offers greater memory but no keyboard-scan hardware, while the MC68HC908JK3E replaces OTPROM with Flash and adds serial interfaces - both require PCB layout changes and firmware porting effort.

Availability

MC68HC705KJ1CP is available at Aetrix Electronics and suitable for industrial sensor interfaces, home appliance control, embedded power supply monitors, and legacy automotive body control requiring stable component supply and long-term lifecycle support.

Supply support for MC68HC705KJ1CP 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 automotive, industrial, and consumer microcontrollers.

The MC68HC705KJ1CP belongs to the M68HC05 family, engineered for cost-sensitive, low-pin-count embedded control applications where OTPROM security, noise immunity, and minimal external components are critical.

FAQ

What is the maximum operating frequency of the MC68HC705KJ1CP?

The MC68HC705KJ1CP operates at a maximum internal frequency of 4.0 MHz when supplied with 5.0 V. This frequency is achieved using the on-chip oscillator with crystal or ceramic resonator; RC oscillator variants (e.g., MC68HRC705KJ1) exhibit temperature- and voltage-dependent variation and are rated lower. The MCU supports fully static operation, meaning it functions correctly down to 0 Hz in stop mode.

Does the MC68HC705KJ1CP support in-circuit programming?

No, the MC68HC705KJ1CP uses OTPROM (one-time programmable read-only memory) and requires parallel programming via the IRQ/VPP pin at 12.5 V. It does not support in-circuit serial programming (ICSP) or Flash-based reprogramming. Programming must be performed before soldering or using a dedicated EPROM programmer with appropriate socket and voltage control.

What I/O features distinguish the MC68HC705KJ1CP from generic 8-bit microcontrollers?

The MC68HC705KJ1CP provides 10-mA sink capability on all 10 I/O pins and 5.5-mA source on six - enabling direct LED and relay driving without external buffers. It also includes hardware keyboard-scan interrupt on PA0–PA3 and software-configurable pulldowns on every I/O pin, reducing BOM count and simplifying mechanical switch interfacing compared to general-purpose MCUs.

Can the MC68HC705KJ1CP operate from a 3.3-V supply?

No, the MC68HC705KJ1CP is specified only for 5.0-V operation per its electrical characteristics (Section 10.5 of Rev. 4.1 datasheet). While related variants like MC68HLC705KJ1 support low-voltage crystal operation, the MC68HC705KJ1CP requires VDD = 5.0 V ± 10%. Using 3.3 V will result in undefined behavior, failed resets, or inability to program OTPROM.

How is EPROM security implemented on the MC68HC705KJ1CP?

The MC68HC705KJ1CP implements EPROM security via a mask option bit that disables external read access to the OTPROM contents after programming. When enabled, attempts to read memory outside the vector area return invalid data. Freescale explicitly states this is a deterrent-not absolute protection-and is intended to raise the barrier against casual copying, not resist sophisticated physical attacks.