MC68HC705C8AB - 8KB OTP 8-Bit HC05 MCU 2.1MHz | NXP | 42-PDIP
MPN: MC68HC705C8AB ✗ Cuối đờiMC68HC705C8AB Tóm tắt
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.
Bộ thay thế dễ dàng lắp đặt cho MC68HC705C8AB — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Các biến thể trong loạt này
Các mẫu cùng loạt có thể lắp đặt dễ dàng tương thích với MC68HC705C8AB (cùng hình factor và footprint) — khác nhau ở Package, Program Memory Size, RAM Size, Supply Voltage, Mounting Type.
MC68HC705C8ACFN
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MC68HC705C8ACB
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MC705C8ABE
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →MCHSC705C8ACFNE
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →MC68HC705C8AB Tỷ lệ tối đa & tính chất điện
| Core | HC05 (M68HC05 family) |
| Bề rộng đường dữ liệu | 8 bit |
| Program Memory Size | 8 KB (8K x 8) OTPROM |
| RAM Size | 304 bytes |
| Tần số xung maksimum | 2.1 MHz |
| Number of I/O Pins | 24 |
| Điện áp cung cấp | 3.3 V or 5 V |
| Oscillator Type | Internal |
| Hộp | 42-PDIP (0.600 in, 15.24 mm) |
| Kiểu lắp đặt | Through-Hole |
| Peripherals | SCI, 16-bit timer (capture/compare) |
| Instruction Set | CISC, fixed instruction set |
| Packaging | Tube |
Cấu hình chân MC68HC705C8AB
| Chân 1 | IRQ — External interrupt request input |
| Chân 2 | TIMER — Timer input capture/output compare |
| Chân 3 | OSC1 — Oscillator input |
| Chân 4 | OSC2 — Oscillator output |
| Chân 5 | PA0 — Port A bit 0 (digital I/O) |
| Chân 6 | PA1 — Port A bit 1 (digital I/O) |
| Chân 7 | PA2 — Port A bit 2 (digital I/O) |
| Chân 8 | PA3 — Port A bit 3 (digital I/O) |
| Chân 9 | PA4 — Port A bit 4 (digital I/O) |
| Chân 10 | PA5 — Port A bit 5 (digital I/O) |
| Chân 11 | PA6 — Port A bit 6 (digital I/O) |
| Chân 12 | PA7 — Port A bit 7 (digital I/O) |
| Chân 13 | PB0 — Port B bit 0 (digital I/O) |
| Chân 14 | PB1 — Port B bit 1 (digital I/O) |
| Chân 15 | PB2 — Port B bit 2 (digital I/O) |
| Chân 16 | PB3 — Port B bit 3 (digital I/O) |
| Chân 17 | PB4 — Port B bit 4 (digital I/O) |
| Chân 18 | PB5 — Port B bit 5 (digital I/O) |
| Chân 19 | PB6 — Port B bit 6 (digital I/O) |
| Chân 20 | VSS — Ground |
| Chân 21 | PB7 — Port B bit 7 (digital I/O) |
| Chân 22 | PC0 — Port C bit 0 (digital I/O) |
| Chân 23 | PC1 — Port C bit 1 (digital I/O) |
| Chân 24 | PC2 — Port C bit 2 (digital I/O) |
| Chân 25 | PC3 — Port C bit 3 (digital I/O) |
| Chân 26 | PC4 — Port C bit 4 (digital I/O) |
| Chân 27 | PC5 — Port C bit 5 (digital I/O) |
| Chân 28 | PC6 — Port C bit 6 (digital I/O) |
| Chân 29 | PC7 — Port C bit 7 (digital I/O) |
| Chân 30 | TxD — SCI transmit data output |
| Chân 31 | RxD — SCI receive data input |
| Chân 32 | RESET — Active-low reset input |
| Chân 33 | TCAP — Timer capture input |
| Chân 34 | TCMP — Timer compare output |
| Chân 35 | NC — Not connected (per datasheet) |
| Chân 36 | NC — Not connected (per datasheet) |
| Chân 37 | NC — Not connected (per datasheet) |
| Chân 38 | NC — Not connected (per datasheet) |
| Chân 39 | NC — Not connected (per datasheet) |
| Chân 40 | VDD — Positive supply voltage (3.3 V or 5 V) |
| Chân 41 | NC — Not connected (per datasheet) |
| Chân 42 | NC — Not connected (per datasheet) |
Ứng dụng tiêu biểu
MC68HC705C8AB phù hợp cho 6 Áp dụngs: 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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho MC68HC705C8AB — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | 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 |
Bảo phân biệt quan trọng
- Pin-compatible across OTP, EPROM, and mask-ROM variants (vsMC68HC705C8ACB vs MC705C8ABE)
- High-speed HSC05 variant available for compute-intensive prototyping (vsMCHSC705C8ACFNE)
- Through-hole PDIP simplifies prototype rework and field service (vsMC68HC705C8ACFN)
- Wide 3.3 V / 5 V supply compatibility (vsModern 3.3 V-only S08 successors)
Ghi chú thiết kế
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.
Thông tin tuân thủ
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.
