MC68HC705C4ACP - 8-bit HC05 MCU 40-Pin DIP | Motorola/Freescale
MPN: MC68HC705C4ACP ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $18.5 | $18.50 |
| 10 | $16.65 | $166.50 |
| 100 | $14.8 | $1,480.00 |
| 500 | $12.95 | $6,475.00 |
| 1,000 | $11.1 | $11,100.00 |
MC68HC705C4ACP Overview
An 8-bit microcontroller (MCU) is a single integrated circuit that combines a processor core, program memory, data memory, and input/output peripherals on one die, sitting at the lowest tier of the embedded processor hierarchy (MCU -> embedded processor -> microprocessor -> system-on-chip). The M68HC05 family was one of the most widely deployed 8-bit controller families of the 1990s, and the 705 C-series variants added user-programmable EPROM for code development and low-volume production.
Key characteristics of the MC68HC705C4ACP include the HC05 HMOS/CMOS-derived low-power CPU architecture, EPROM program memory suitable for development and field-update-tolerant designs, through-hole 40-pin DIP mounting for prototyping-friendly board designs, and industrial temperature grade operation for factory-floor environments. The C4A variant integrates a timer system and bidirectional I/O ports typical of the HC705C family.
From a technical standpoint, the device uses the HC05 instruction set, which is a compact, accumulator-based 8-bit architecture with memory-mapped I/O, making peripheral access straightforward. The EPROM-based memory requires an external programming voltage during development, and the A-suffix devices in this family refined several electrical characteristics over the original C4. Clock generation is typically provided by an on-chip oscillator with an external crystal or ceramic resonator.
Typical applications include industrial control panels, appliance controllers, automotive body electronics, security systems, and legacy test equipment — anywhere a simple, deterministic 8-bit controller in a through-hole package is required. Its DIP package makes it especially common in legacy repair, spare-part harvesting, and repair of 1990s-era equipment.
Design consideration: since this device is long discontinued (NRND/EOL from Freescale/NXP), new designs should evaluate MC9S08-family successors, while existing systems should plan lifecycle management through excess-stock and aftermarket sourcing.
This page synthesizes distributor availability data, family drop-in alternatives, and legacy-sustainment design notes not found in the original Motorola datasheet, providing a single reference point for engineers maintaining HC05-based systems.
Drop-in alternatives for MC68HC705C4ACP — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MC68HC705C4ACP (same form factor and footprint) — differing in Core Architecture, Program Memory Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MC68HC705C8ACP
✅ Drop-In📋 Reference alternative (not in catalog)
MC705C8ACPE
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC705C9ACP
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC908GP32CBE
✅ Drop-In✓ In Stock
$4.45 / Unit
View Datasheet →MC68HC705C4ACP Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit HC05 (M68HC05 Family) |
| Product Series | MC68HC705C4A (EPROM variant, A-suffix) |
| Program Memory Type | EPROM (one-time programmable) |
| Package | 40-pin DIP (Dual In-line Package) |
| Package Shape | Rectangular |
| Terminal Form | Through-Hole |
| Number of Terminals | 40 |
| Temperature Grade | Industrial |
| Design Strategy | Motorola CSIC (Customer-Specified Integrated Circuit) |
| Mounting Type | Through-Hole |
| Lifecycle Status | Obsolete / Not Recommended for New Design (NXP heritage part) |
MC68HC705C4ACP rectangular Pin Configuration Guide
Pin configuration for MC68HC705C4ACP (rectangular package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for MC68HC705C4ACP.
Refer to the datasheet for full pin configuration.
Typical Applications
MC68HC705C4ACP is suitable for 6 applications: Legacy Industrial Control Repair, Appliance and White-Goods Controllers, Security and Access Control Systems, Automotive Body and Comfort Electronics, Test Equipment and Instrumentation Firmware Boards, IoT Legacy Node Retrofit Front-Ends.
Legacy Industrial Control Repair
The MC68HC705C4ACP fits industrial control panel repair because it preserves both the 40-pin through-hole DIP footprint and the exact HC05 firmware environment of 1990s-era controllers. Its industrial temperature grade matches factory-floor cabinets, and the EPROM memory retains the original control logic. In a repair workflow, a stock device is programmed with a verified EPROM image from a healthy unit and socketed in place of the failed controller, restoring deterministic 8-bit control behavior without PCB rework. Because EPROM is one-time programmable, keep several pre-programmed spares per equipment model, and verify date codes on broker-sourced stock since 20-plus-year-old devices can suffer programming-window drift.
Recommended
Appliance and White-Goods Controllers
Appliance main boards from the 1990s commonly used HC705 family MCUs for wash-cycle sequencing, temperature monitoring, and keypad scanning. The MC68HC705C4ACP's simple accumulator-based 8-bit core, memory-mapped I/O, and generous 40-pin DIP I/O budget cover motor-relay driving, sensor polling, and display multiplexing in one through-hole part. For appliance service organizations, this MCU enables board-level repair of out-of-production dishwashers, washing machines, and ovens. The key performance consideration is that EPROM must be programmed off-board with the correct programming voltage — plan a programming station with known-good firmware images, and confirm the oscillator configuration (crystal versus ceramic resonator) matches the original board timing.
Recommended
Security and Access Control Systems
Standalone access-control keypads, alarm panels, and card-reader interfaces of the HC05 generation relied on the MC68HC705C4ACP class of devices: an 8-bit core executing fixed EPROM logic, polling keypad matrices and driving relays and indicators through the 40-pin DIP's I/O ports. The device's industrial temperature grade supports outdoor cabinet electronics, and its deterministic instruction timing simplifies watchdog and anti-tamper sequencing. When sustaining such systems, the main engineering consideration is firmware custody — EPROM cannot be re-read-and-rewritten casually, so maintain a golden-image archive per panel revision. Replacement devices must be programmed with the identical vector table layout or the system will fail to boot after swap.
Recommended
Automotive Body and Comfort Electronics
1990s automotive body controllers — window lift modules, mirror controllers, seat-memory units, and climate heads — were frequently built on HC05 family devices with automotive-grade temperature ranges. While the MC68HC705C4ACP variant itself is industrial-graded, its architecture is representative of the controllers found in vehicle harness modules, and it appears in bench-test fixtures and ECU development rigs of that era. Its 40-pin through-hole DIP makes it ideal for emulator and breadboard fixtures used when diagnosing original automotive HC05 boards. When servicing such systems, account for the automotive supply environment (load-dump transients) by keeping the original board-level protection circuitry intact around the MCU socket.
Recommended
Test Equipment and Instrumentation Firmware Boards
Bench instruments and measurement fixtures from the mid-1990s used HC705 devices for front-panel control, range switching, and IEEE-style handshaking glue logic. The MC68HC705C4ACP's memory-mapped I/O and cycle-deterministic core make it suitable for sequencer boards where timing behavior must be repeatable across repairs. Its DIP packaging allows socketed installation in instrumentation backplanes, enabling field firmware changes by swapping pre-programmed devices. Engineering consideration: document the exact oscillator frequency on the original board because instrument timing loops are often cycle-counted against it; a resonator-to-crystal substitution can shift timing loops by several percent and break calibration routines.
Recommended
IoT Legacy Node Retrofit Front-Ends
When retrofitting connectivity onto legacy HC05-based machines, the MC68HC705C4ACP often remains as the deterministic real-time front-end (sensor polling, actuator sequencing) while a modern companion MCU or module adds wireless connectivity. In this split-architecture approach, the original HC705 keeps its EPROM logic untouched, minimizing certification and behavior risk, while the new node handles protocol translation. Design the interface as a simple UART or GPIO handshake so the original firmware needs no modification. The key consideration is level compatibility: the HC705's 5V CMOS I/O requires level shifting toward 3.3V modules, and the industrial temperature grade of the C4ACP keeps the front-end valid across the same environmental envelope as the original installation.
Recommended
Recommended Products Summary
Engineering reference data for MC68HC705C4ACP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC68HC705C8ACP | MC705C8ACPE | MC68HC705C9ACP | MC908GP32CBE |
|---|---|---|---|---|---|
| Package | 40-pin DIP (through-hole) | 40-pin DIP - same | 40-pin DIP - same | 40-pin DIP - same | 40-pin DIP - same |
| Brand | Motorola / NXP Semiconductors (heritage) | Motorola / Freescale / NXP | Freescale / NXP | Motorola / Freescale | Motorola / Freescale / NXP |
| CPU Core | HC05 8-bit | HC05 8-bit | HC05 8-bit | HC05 8-bit | HC08 8-bit (upward-compatible) |
| Program Memory | EPROM, ~4 KB class | EPROM, ~8 KB class | EPROM, ~8 KB class | EPROM, ~15.5 KB class | Flash, ~32 KB class |
| Memory Technology | One-time programmable EPROM | One-time programmable EPROM | One-time programmable EPROM | One-time programmable EPROM | Reprogrammable Flash |
| Temperature Grade | Industrial | Industrial | Industrial | Industrial | Industrial |
| RoHS Compliance | No (legacy leaded process era) | No | Yes (E suffix per NXP) | No | Yes |
| Lifecycle Status | Obsolete | Obsolete | NRND (purchasable per NXP community) | Obsolete | NRND / legacy |
Key Differentiators
- Exact legacy footprint preservation (vs MC908GP32CBE)
- RoHS-compliant family option exists (vs MC68HC705C8ACP)
- Smallest memory in family means lowest cost per repair where code fits (vs MC68HC705C9ACP)
Design Notes
EPROM programming is one-time: the MC68HC705C4ACP cannot be erased and reprogrammed like flash. Before committing a stock device to the programming socket, validate the firmware image on an emulator or a sacrificial device. Check that the programming voltage supply is stable and within the datasheet window — 20-plus-year-old EPROM parts have narrower effective programming margins, and under-programmed bits may fail after weeks in the field. Always burn and functionally verify the vector table locations last, as is standard HC705 EPROM practice.
When substituting the larger-memory family members (MC68HC705C8ACP, MC68HC705C9ACP), remap the firmware's vector table and verify the RAM boundary addresses. Stack behavior and any absolute-addressed variables that live near the top of the C4A memory map will move on the larger devices. Re-run the full functional test suite on the replacement device rather than assuming core compatibility guarantees application correctness — peripheral register locations are largely consistent but timing loop constants calibrated to the original bus frequency must be re-validated.
Observe supply decoupling discipline on the 40-pin DIP: fit a 100 nF ceramic capacitor directly across the VDD/VSS pins plus bulk capacitance at the board entry. HC05 devices generate rail noise on internal clock edges, and legacy boards often used long socket traces that add inductance. Estimated: a 0.1 uF capacitor with 20 nH of trace inductance resonates near 100 MHz, so it remains effective for HC05 edge rates, but aged electrolytics on 1990s boards commonly measure far below nominal — replace bulk capacitors during any MCU socket-level repair.
Use a socket rather than direct soldering for this obsolete part. A machined-pin or dual-wipe socket protects the 20-plus-year-old device from thermal stress during installation and enables future swaps without desoldering. For industrial environments, add a pull-up on RESET and an RC power-on-reset network if the original board lacks brown-out protection, since HC05-class parts have no internal reset supervisor on this generation.
Compliance Information
Original HC705C4A DIP predates RoHS; NXP community documentation indicates the E-suffix family successor (MC705C8ACPE) was created specifically to add RoHS compliance, confirming the legacy version's non-compliant leaded construction.
