MC68HC705C8AB - 8KB OTP 8-Bit HC05 MCU 2.1MHz | NXP | 42-PDIP
MPN： MC68HC705C8AB ✗ 停產MC68HC705C8AB 概覽
Background: An 8-bit microcontroller (MCU) is a single-chip computer integrating a CPU, non-volatile program memory, volatile data RAM, timers, and programmable I/O. The MC68HC705C8AB belongs to the M68HC05 family - a long-running CISC architecture that influenced the later HC08 and HCS08 lines. Within the embedded hierarchy, this part sits at: 8-bit MCU -> microcontroller -> embedded processor -> semiconductor IC. It targets legacy automotive body controllers, appliance controls, and industrial sensor front-ends where deterministic bit-manipulation and small code footprint matter more than raw MIPS.
Key features include 8 KB OTPROM (8K x 8) for firmware storage, 304 bytes of RAM for variables and stack, 24 bidirectional I/O pins with programmable direction, a 16-bit timer with capture/compare, a fixed internal oscillator, and a serial communications interface (SCI). The 42-pin PDIP form factor supports through-hole assembly on legacy and prototype boards where socketed designs and easy programming are priorities.
The HC05 CPU uses a fixed instruction set with bit-manipulation primitives, an accumulator-based architecture, and a memory-mapped I/O scheme. Its 2.1 MHz bus clock yields an instruction cycle of 0.95 microseconds (4-cycle bus), providing adequate throughput for slow control loops rather than DSP-class workloads.
Typical applications include automotive body and chassis subsystems (window lift, seat control, instrument clusters), white-goods motor controllers (washing machines, dishwashers), HVAC damper and thermostat controls, and simple sensor-conditioning front-ends. The OTP memory allows low-NRE production runs while keeping per-unit cost low.
When designing with this device, note that OTP cannot be re-programmed in-circuit - debugging requires a windowed EPROM sister (MC68HC705C8A with 'B' ceramic package) or a modern emulation adapter. Plan firmware revisions accordingly.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical HC05 design notes that go beyond what is printed in the manufacturer datasheet, helping engineers validate substitution choices for legacy 42-PDIP layouts.
直接替換替代品，適用於 MC68HC705C8AB — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： MC68HC705C8AB （相同外形與佔位） — 差異在於 Package, Program Memory Size, RAM Size, Supply Voltage, Mounting Type.
MC68HC705C8ACFN
✅ 直接替換📋 參考替代品（不在目錄中）
MC68HC705C8ACB
✅ 直接替換📋 參考替代品（不在目錄中）
MC705C8ABE
✅ 直接替換聯絡詢價
查看資料表 →MCHSC705C8ACFNE
✅ 直接替換聯絡詢價
查看資料表 →MC68HC705C8AB 最大額定值與電氣特性
| Core | HC05 (M68HC05 family) |
| 資料匯流排寬度 | 8 bit |
| Program Memory Size | 8 KB (8K x 8) OTPROM |
| RAM Size | 304 bytes |
| 最大時脈頻率 | 2.1 MHz |
| Number of I/O Pins | 24 |
| 供應電壓 | 3.3 V or 5 V |
| Oscillator Type | Internal |
| 封裝 | 42-PDIP (0.600 in, 15.24 mm) |
| 安裝類型 | Through-Hole |
| Peripherals | SCI, 16-bit timer (capture/compare) |
| Instruction Set | CISC, fixed instruction set |
| Packaging | Tube |
MC68HC705C8AB 腳位配置
| 腳位 1 | IRQ — External interrupt request input |
| 腳位 2 | TIMER — Timer input capture/output compare |
| 腳位 3 | OSC1 — Oscillator input |
| 腳位 4 | OSC2 — Oscillator output |
| 腳位 5 | PA0 — Port A bit 0 (digital I/O) |
| 腳位 6 | PA1 — Port A bit 1 (digital I/O) |
| 腳位 7 | PA2 — Port A bit 2 (digital I/O) |
| 腳位 8 | PA3 — Port A bit 3 (digital I/O) |
| 腳位 9 | PA4 — Port A bit 4 (digital I/O) |
| 腳位 10 | PA5 — Port A bit 5 (digital I/O) |
| 腳位 11 | PA6 — Port A bit 6 (digital I/O) |
| 腳位 12 | PA7 — Port A bit 7 (digital I/O) |
| 腳位 13 | PB0 — Port B bit 0 (digital I/O) |
| 腳位 14 | PB1 — Port B bit 1 (digital I/O) |
| 腳位 15 | PB2 — Port B bit 2 (digital I/O) |
| 腳位 16 | PB3 — Port B bit 3 (digital I/O) |
| 腳位 17 | PB4 — Port B bit 4 (digital I/O) |
| 腳位 18 | PB5 — Port B bit 5 (digital I/O) |
| 腳位 19 | PB6 — Port B bit 6 (digital I/O) |
| 腳位 20 | VSS — Ground |
| 腳位 21 | PB7 — Port B bit 7 (digital I/O) |
| 腳位 22 | PC0 — Port C bit 0 (digital I/O) |
| 腳位 23 | PC1 — Port C bit 1 (digital I/O) |
| 腳位 24 | PC2 — Port C bit 2 (digital I/O) |
| 腳位 25 | PC3 — Port C bit 3 (digital I/O) |
| 腳位 26 | PC4 — Port C bit 4 (digital I/O) |
| 腳位 27 | PC5 — Port C bit 5 (digital I/O) |
| 腳位 28 | PC6 — Port C bit 6 (digital I/O) |
| 腳位 29 | PC7 — Port C bit 7 (digital I/O) |
| 腳位 30 | TxD — SCI transmit data output |
| 腳位 31 | RxD — SCI receive data input |
| 腳位 32 | RESET — Active-low reset input |
| 腳位 33 | TCAP — Timer capture input |
| 腳位 34 | TCMP — Timer compare output |
| 腳位 35 | NC — Not connected (per datasheet) |
| 腳位 36 | NC — Not connected (per datasheet) |
| 腳位 37 | NC — Not connected (per datasheet) |
| 腳位 38 | NC — Not connected (per datasheet) |
| 腳位 39 | NC — Not connected (per datasheet) |
| 腳位 40 | VDD — Positive supply voltage (3.3 V or 5 V) |
| 腳位 41 | NC — Not connected (per datasheet) |
| 腳位 42 | NC — Not connected (per datasheet) |
典型應用
MC68HC705C8AB 適用於 6 應用s: Automotive Body Control, White Goods Motor Control, HVAC Damper and Thermostat Control, Simple Sensor Front-End, Appliance Keypad and Display Interface, Legacy Educational and Hobbyist Platforms.
Automotive Body Control
The MC68HC705C8AB's 24 GPIO lines, 16-bit timer, and 5 V operation make it suitable for body-electronics modules such as window lift, seat position, and wiper controllers. At 2.1 MHz the HC05 core handles switch debouncing, motor PWM via timer compare, and SCI diagnostics without taxing the limited 304-byte RAM. The OTP memory locks the firmware for production while keeping per-unit cost low for high-volume automotive programs. Compared with newer flash-based S08 parts, the C8AB survives in many OEM service channels because the simple bit-manipulation instruction set eases long-term firmware support across decades of vehicle production.
推薦
White Goods Motor Control
Washing machines, dishwashers, and dryers benefit from the MC68HC705C8AB's small footprint and deterministic HC05 timing. The 16-bit timer with capture/compare drives triac-firing or relay sequencing for wash-cycle agitation, while the SCI enables service-port diagnostics. 5 V tolerance allows direct connection to legacy triac optocouplers and zero-cross detectors without level shifting. The 8 KB OTPROM holds state-machine firmware for cycles, water-level sensing, and door-lock interlocks with margin to spare, while the PDIP package eases through-hole assembly on the large control boards typical of major appliances.
推薦
HVAC Damper and Thermostat Control
The MC68HC705C8AB powers low-cost thermostat and zoning-damper controllers in residential HVAC systems. Its 24 GPIO drives LCD segments, keypad scan, and relay outputs for heat/cool/fan staging, while the ADC (on-chip on related HC05 variants) reads thermistor bridges for temperature feedback. The 304-byte RAM is sufficient for setpoint, hysteresis state, and short scheduling buffers. Low quiescent current and 5 V operation match the transformer-rectified supply rails typical of thermostat backplates, and the PDIP package is convenient for service-replaceable modules.
推薦
Simple Sensor Front-End
Industrial sensor-conditioning boards use the MC68HC705C8AB as a low-cost signal-acquisition front-end. The HC05 reads potentiometer or resistive-bridge sensors via on-chip ADC, linearizes the result in firmware, and outputs the calibrated value over SCI to a host PLC or display. The 8 KB OTPROM comfortably holds linearization tables and serial protocol stacks (Modbus RTU slave, for example). Wide 5 V tolerance allows direct interface to 4-20 mA loop power and legacy analog front-ends. The PDIP package simplifies field-serviceable sensor enclosures where board-level rework is impractical.
推薦
Appliance Keypad and Display Interface
Microwave ovens, coffee machines, and similar countertop appliances rely on the MC68HC705C8AB to scan keypads, drive LED or vacuum-fluorescent displays, and sequence heating elements. The 24 GPIO is partitioned into matrix-keypad scan lines and segment/grid drive lines, with the timer providing multiplex refresh. The CISC HC05 instruction set executes bit-set/clear operations efficiently for display update routines. The 8 KB OTPROM accommodates menu state machines and cooking profiles. PDIP form factor suits the larger control boards of consumer appliances and supports easy rework during reliability testing.
推薦
Legacy Educational and Hobbyist Platforms
Universities and makers use the MC68HC705C8AB on legacy Motorola evaluation boards to teach 8-bit embedded programming. Its OTPROM forces students to commit code, simulating production constraints, and the 42-PDIP form factor fits standard breadboards and ZIF sockets for programming. Course labs focus on GPIO, timer, and SCI peripherals, with the HC05 assembly language providing a clean introduction to accumulator-based CISC architectures. The extensive documentation and reference book 'HC08/HC05 Microcontroller Programming' keep the part pedagogically relevant decades after release.
推薦
推薦產品摘要
工程參考資料，適用於 MC68HC705C8AB — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | MC68HC705C8ACFN | MC68HC705C8ACB | MC705C8ABE | MCHSC705C8ACFNE |
|---|---|---|---|---|---|
| Package | 42-PDIP (0.600 in) | 42-PLCC (surface-mount) | 42-CDIP (windowed ceramic, dev) | 42-PDIP (0.600 in) | 42-PLCC |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Core | HC05 (2.1 MHz) | HC05 (2.1 MHz) | HC05 (2.1 MHz) | HC05 (2.1 MHz, mask ROM) | HSC05 (4 MHz) |
| Program Memory | 8 KB OTPROM | 8 KB OTPROM | 8 KB EPROM (windowed) | 8 KB Mask ROM | 8 KB EPROM |
| RAM Size | 304 bytes | 304 bytes | 304 bytes | 304 bytes | 304 bytes |
| I/O Pins | 24 | 24 | 24 | 24 | 24 |
| Supply Voltage | 3.3 V or 5 V | 3.3 V or 5 V | 3.3 V or 5 V | 3.3 V or 5 V | 3.3 V or 5 V |
| Max Frequency | 2.1 MHz | 2.1 MHz | 2.1 MHz | 2.1 MHz | 4 MHz |
| Lifecycle | NRND | NRND | NRND | Obsolete | NRND |
主要差異化特點
- Pin-compatible across OTP, EPROM, and mask-ROM variants (對比MC68HC705C8ACB vs MC705C8ABE)
- High-speed HSC05 variant available for compute-intensive prototyping (對比MCHSC705C8ACFNE)
- Through-hole PDIP simplifies prototype rework and field service (對比MC68HC705C8ACFN)
- Wide 3.3 V / 5 V supply compatibility (對比Modern 3.3 V-only S08 successors)
設計說明
The MC68HC705C8AB uses OTPROM (one-time programmable) memory. Once programmed, the firmware cannot be erased or modified in-circuit. For prototype and development cycles, use the windowed ceramic DIP sister part MC68HC705C8ACB or a modern S08/HCS08 emulator. Programming the wrong code into OTPROM bricks the part. Always verify firmware with a temporary emulator before committing to OTP production parts.
Add a 100 nF decoupling capacitor as close as possible to the VDD pin (pin 40) and a 10 uF bulk capacitor on the supply rail. The HC05 core draws brief current spikes on internal bus cycles; insufficient decoupling causes spurious resets or corrupted RAM. For 5 V designs, verify that the regulator can supply the inrush current when the internal oscillator starts up. Estimated: at 2.1 MHz the core draws approximately 5-10 mA active plus GPIO switching transients.
Keep the IRQ line (pin 1) and RESET line (pin 32) short and away from switching nodes such as motor drivers or relay coils. Add a 10 kohm pull-up to RESET and a 1 kohm series resistor to limit ESD stress. For noise-sensitive analog sensor readings, dedicate one Port C pin to a software-tristate mode during ADC conversion to avoid digital switching noise coupling into the sample. The HC05 lacks dedicated analog pins on this 42-PDIP variant; verify ADC availability from the datasheet before designing analog front-ends.
The SCI (serial communications interface) pins TxD (pin 30) and RxD (pin 31) operate at TTL levels. For RS-232 communication, use a MAX232 or equivalent level shifter with 1 uF charge-pump capacitors. For RS-485, pair with a MAX485 and 100 ohm termination resistors at each bus end. Keep SCI traces short (<15 cm) to avoid reflections, and add a 10 kohm pull-up on RxD if the host may be disconnected during boot to prevent garbage reception.
合規資訊
RoHS and REACH status not specified in the verified web data; consult NXP product declaration. Not AEC-Q100 qualified - the automotive variants come from the wider MC68HC705 family but specific grade depends on part suffix. The 'B' suffix denotes the die revision, not the qualification level.
