MCHRC705KJ1CPE - 8-bit HC05 MCU, 4MHz, 1.2KB OTP | NXP
MPN: MCHRC705KJ1CPE ✗ End of LifeMCHRC705KJ1CPE Overview
A microcontroller unit (MCU) is a single-chip embedded processor that integrates a CPU core, program and data memory, and peripherals on one die. Within the semiconductor hierarchy, the HC05 belongs to the 8-bit microcontroller class, positioned below 16-bit and 32-bit MCUs but prized for simplicity, deterministic behavior, and low cost in fixed-function embedded control. One-time programmable (OTP) program memory is a memory type that can be programmed once in the field or in production and cannot be erased, distinguishing it from EPROM (UV-erasable) and Flash (electrically erasable) variants.
Key features of the MCHRC705KJ1CPE include the proven HC05 8-bit core running at 4 MHz, 1.2KB OTP program memory for firmware that is fixed at production programming, 64 bytes of on-chip RAM, and on-chip peripherals consisting of a power-on reset (POR) and a watchdog timer (WDT) for robust fault recovery. The 10 I/O lines provide sufficient connectivity for small control tasks such as driving LEDs, reading switches, or simple serial bit-banged communication.
Technically, the HC05 architecture uses an accumulator-based instruction set with fully static logic, allowing clock speeds down to DC for ultra-low-power designs. The supply voltage range spans 3V upward per the listing, supporting both 3.3V and 5V legacy systems. The POR ensures predictable startup, while the WDT guards against software lockup in unattended equipment.
Typical applications include small home appliances, low-cost industrial timers, consumer electronics control panels, and legacy-equipment service replacement, where firmware is finalized and OTP memory keeps unit cost minimal.
When designing with this device, note that OTP memory cannot be reprogrammed; reserve development for the windowed or emulation variants of the HC705KJ1 family and commit only verified firmware to production silicon.
This page synthesizes verified distributor data, drop-in alternatives, and practical design notes for an obsolete part - information not consolidated in any single datasheet. Pricing and availability as of 2026-10-18.
Drop-in alternatives for MCHRC705KJ1CPE — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
MC68HC705KJ1CP
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68HC05KJ1CP
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68HC705KJ1P
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MCHRC705KJ1CPE
✅ Drop-InContact for price
View Datasheet →MCHRC705KJ1CPE Maximum Ratings & Electrical Characteristics
| Core Processor | HC05 |
| Core Size | 8-Bit |
| Maximum Clock Speed | 4 MHz |
| Program Memory Size | 1.2KB (1.2K x 8) |
| Program Memory Type | OTP |
| RAM Size | 64 x 8 |
| EEPROM Size | None |
| Number of I/O | 10 |
| Peripherals | POR, WDT |
| Connectivity | None (no on-chip serial peripherals) |
| Supply Voltage (Vcc/Vdd) | 3V and higher |
| Package | 16-PDIP (0.300 inch, 7.62 mm) |
| Mounting Type | Through-Hole |
| Series | HC05 |
| Part Status | Obsolete (supplied by Rochester Electronics as authorized aftermarket) |
MCHRC705KJ1CPE 16-pdip (0.300 inch, 7.62 mm) Pin Configuration Guide
Pin configuration for MCHRC705KJ1CPE (16-pdip (0.300 inch, 7.62 mm) 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 MCHRC705KJ1CPE.
Refer to the datasheet for full pin configuration.
Typical Applications
MCHRC705KJ1CPE is suitable for 6 applications: Small Appliance Control, Industrial Timers and Sequencers, Consumer Electronics Keypad Controllers, Battery-Powered Portable Devices, Automotive Body Accessory Modules (Legacy Service), Educational and Hobby Embedded Training.
Small Appliance Control
The MCHRC705KJ1CPE suits small-appliance controllers such as coffee makers, fans, and hair dryers, where the control algorithm is fixed at production and unit cost dominates. Its 10 I/O lines drive relays, triacs via logic, LEDs, and read push buttons or thermostats without external glue logic, while the 4 MHz HC05 core executes simple state machines with predictable timing. The on-chip power-on reset guarantees a clean start after mains interruptions, and the watchdog timer recovers the system from firmware lockups - important in unattended mains-powered products. Because program memory is OTP, firmware is finalized before mass programming, eliminating flash in-circuit reprogramming circuitry and cost. For repair of existing appliances this DIP-16 part is socket-replaceable; for new appliance designs a Flash MCU is strongly recommended due to the obsolete status of the HC705KJ1 family.
Recommended
Industrial Timers and Sequencers
In simple industrial timers, pump sequencers, and time-delay relay modules, the MCHRC705KJ1CPE provides deterministic 8-bit control with a watchdog timer that guarantees recovery from transient faults in electrically noisy factory environments. Ten I/O lines interface rotary switches, DIP switches, optocoupler inputs, and relay drivers directly, while the fully static HC05 core allows clock throttling down to DC for very low standby consumption between timing events. The 64 bytes of RAM are sufficient for BCD time counters and state flags in fixed-function sequencers. Through-hole 16-PDIP packaging simplifies hand rework and field servicing of panel-mounted timer boards. Because OTP memory cannot be corrected after programming, verify timing firmware on an emulation device before committing production units, and source spares now given the part's obsolete lifecycle status.
Recommended
Consumer Electronics Keypad Controllers
Keypad scanning, LED indication, and simple IR command decoding in low-cost consumer electronics map well onto the MCHRC705KJ1CPE: the 10 I/O lines can be multiplexed into a 4x3 keypad matrix with two spare lines for status LEDs or IR receiver input. The 4 MHz HC05 core executes polling loops and software debouncing with ample margin, and the 1.2KB OTP program memory accommodates matrix scan, decode, and output logic comfortably. The power-on reset peripheral ensures the controller always starts in a known state after battery insertion, and the watchdog protects against firmware hangs in devices that may be dropped or electrostatically stressed. DIP-16 packaging enables low-cost single-sided boards typical of this product class. Legacy remote controls and small appliances built on this MCU remain serviceable with Rochester Electronics authorized stock.
Recommended
Battery-Powered Portable Devices
The MCHRC705KJ1CPE fits battery-operated toys, meters, and portable indicators that benefit from the fully static HC05 core, which tolerates clock frequencies down to DC so the MCU can be stopped between tasks at near-zero current. Operation from a 3V supply allows direct powering from two alkaline cells without a regulator in the low-voltage operating mode, and the 64-byte RAM plus compact instruction set keep active duty cycles short. Ten I/O lines handle push buttons, LED indicators, and a small piezo buzzer with no external logic. The OTP program memory is programmed once at production, which is acceptable for fixed-function toys and novelty devices. Designers should derate the maximum 4 MHz clock at reduced supply voltage per the family datasheet, and note the obsolete status when planning multi-year product roadmaps.
Recommended
Automotive Body Accessory Modules (Legacy Service)
Many 1990s-era automotive accessory modules - mirror controllers, seat memory units, and simple body convenience functions - were built on HC05 KJ-series MCUs, and the MCHRC705KJ1CPE is used to service these boards during repair. The POR and WDT peripherals support the reset discipline needed in vehicles, and the through-hole 16-PDIP package allows direct socket replacement in legacy module PCBs. The 10 I/O lines interface switch packs, lamp drivers, and relay coils with minimal external circuitry, and the 4 MHz core handles polling-based control loops with deterministic behavior. Because the part is obsolete, repair shops should stock quantities from Rochester Electronics authorized aftermarket supply. Note that OTP firmware must match the original module program; units are typically programmed from archived production images rather than redeveloped.
Recommended
Educational and Hobby Embedded Training
The 16-PDIP through-hole MCHRC705KJ1CPE is practical for embedded-systems training on classic 8-bit architecture: the socketed DIP package permits repeated insertion in breadboards and training boards, the HC05 instruction set teaches accumulator-based programming fundamentals, and the simple memory map (1.2KB OTP, 64 bytes RAM) makes internal operation transparent to students. The POR and WDT peripherals demonstrate real-world reliability mechanisms, and the 10 I/O lines support LED, switch, and seven-segment laboratory exercises. Programming requires an HC705-family gang or development programmer targeting OTP parts, typically paired with an emulation device during coursework. Because the family is obsolete, courses should treat it as a legacy-architecture case study while using a current Flash MCU, such as a PIC or AVR DIP device, as the primary hands-on platform.
Recommended
Recommended Products Summary
Engineering reference data for MCHRC705KJ1CPE — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC68HC705KJ1CP | MC68HC05KJ1CP | MCHRC705KJ1CPE (Rochester build) |
|---|---|---|---|---|
| Brand | NXP Semiconductors (Freescale) | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors / Rochester Electronics |
| Package | 16-PDIP (0.300 inch, 7.62 mm) | 16-PDIP - same | 16-PDIP - same | 16-PDIP - same |
| Core / Bit Width | HC05 8-bit | HC05 8-bit | HC05 8-bit | HC05 8-bit |
| Max Clock Speed | 4 MHz | 4 MHz | 4 MHz | 4 MHz |
| Program Memory | 1.2KB OTP | 1.2KB OTP | 1.2KB Masked ROM | 1.2KB OTP |
| RAM | 64 x 8 | 64 x 8 | 64 x 8 | 64 x 8 |
| I/O Count | 10 | 10 | 10 | 10 |
Key Differentiators
- User-programmable OTP memory (vs MC68HC05KJ1CP)
- Authorized aftermarket availability (vs Original NXP production (discontinued))
- Peripherals on-chip (vs MC68HC705KJ1CP)
Design Notes
OTP program memory is a one-shot resource: a single programming error renders the device unusable. Always validate firmware on the emulation or windowed-EPROM variant of the HC705KJ1 family before committing OTP production units, and program from an archived, checksum-verified image. Since the part is obsolete, compute total lifetime quantity needs and place a last-time-buy with Rochester Electronics authorized stock; independent-distributor inventory (e.g., 2,752 pieces at Heisener) is finite and unverified for authenticity.
The HC05 core is fully static, so the oscillator can be stopped or slowed to DC between tasks to save current in battery applications. Operate at 5V nominal for the full 4 MHz rating; if running from a 3V source, verify the reduced-frequency derating curve in the family datasheet before fixing the crystal value. Include 100 nF decoupling directly at the Vdd/Vss pins and keep the reset pin properly biased via the internal POR plus an external RC for noisy environments.
In the 16-PDIP through-hole package, place the crystal or ceramic resonator across OSC1/OSC2 as close to the pins as possible with short ground returns to minimize stray capacitance. Route the /IRQ line away from relay and triac drive traces, and use the watchdog timer as the last line of defense against firmware lockup induced by mains-borne transients in appliance and industrial products. For socketed legacy repairs, clean socket contacts to avoid intermittent reset behavior.
Compliance Information
Compliance data not present in the verified web data. As a legacy 16-PDIP part originally released before RoHS, tin-lead plating is possible - confirm with the supplier before ordering.
