PIC17C42A-25E/P - 8.25 MIPS 8-bit OTP MCU, 4KB, 25MHz, 40-DIP | Microchip
MPN: PIC17C42A-25E/P ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.85 | $9.85 |
| 10 | $8.9 | $89.00 |
| 100 | $7.55 | $755.00 |
| 500 | $6.42 | $3,210.00 |
| 1,000 | $5.6 | $5,600.00 |
PIC17C42A-25E/P Overview
An 8-bit OTP microcontroller (One-Time-Programmable MCU) is a class of microcontrollers whose on-chip program memory can be written exactly once and then behaves like masked ROM. The PIC17C42A belongs to Microchip's PIC17C family, which sits at the top of the original 8-bit PIC hierarchy (PIC12CXXX < PIC16C5X/PIC16CXX < PIC17C4X) and is upwards compatible with the PIC16C5X, PIC12CXXX and PIC16CXX instruction sets, extending them with a hardware multiplier, additional interrupt sources, and a wider 16-bit instruction path.
Key features include a RISC architecture with only 58 single-word instructions, an 8-bit data path with a 16-bit instruction word for compact code density, a hardware 8-bit x 8-bit multiplier, an external oscillator interface, and brown-out / watchdog / power-on reset peripherals typical of the family. The 17C-series instruction set adds multiply, table-read, table-write, and 16-bit MOV/MOVFP/MOVPF operations not present in earlier PIC16 cores, allowing faster arithmetic and pointer-heavy code.
The PIC17C42A is implemented in CMOS technology with on-chip EPROM-based program storage. Because it is OTP rather than flash, the device is targeted at production volume code that does not require field updates, and is frequently used as a cost-down replacement for older masked-ROM MCUs. The PIC17C4X family shares peripheral architecture with later PIC18F devices, making PIC18F migration a well-documented path.
Typical applications include industrial control, motor control, automotive body and chassis ECUs, sensor interfacing, and consumer appliance control. The 33 I/O pins and 232-byte RAM suit designs that need more I/O than PIC16 mid-range parts can offer while keeping the simplicity of an 8-bit core.
When designing with this device, remember that OTP memory cannot be erased; engineers typically validate firmware on a flash-based PIC18F or PIC17C development part and then move the final code image to the PIC17C42A for production. Always provide adequate decoupling on VDD and place the external oscillator close to the OSC1/OSC2 pins to meet the 25 MHz timing budget.
This page synthesizes distributor stock, drop-in alternatives in the same 40-pin PDIP footprint, and engineering design notes beyond the manufacturer datasheet.
Drop-in alternatives for PIC17C42A-25E/P — 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 PIC17C42A-25E/P (same form factor and footprint) — differing in Package, Program Memory Type, Core Architecture, Operating Temperature Range, Mounting Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC17C42A-25/PT
✅ Drop-In✓ In Stock
$5.55 / Unit
View Datasheet →PIC17C42A-16E/P
✅ Drop-In✓ In Stock
$5.85 / Unit
View Datasheet →PIC17C42A-16/P
✅ Drop-In✓ In Stock
$7.45 / Unit
View Datasheet →PIC17C42A-25E/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC17C42A-25E/P Maximum Ratings & Electrical Characteristics
| Family | PIC17C |
| Core | 8-bit PIC RISC |
| Instruction Set Width | 16-bit |
| Number of Instructions | 58 single-word |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 4 KB (2K x 16) |
| RAM Size | 232 x 8 bytes |
| EEPROM | None (no on-chip data EEPROM) |
| Maximum CPU Clock | 25 MHz |
| Performance | 8.25 MIPS (121 ns instruction cycle) |
| I/O Pins | 33 |
| Supply Voltage (VDD) | 4.5 V to 5.5 V |
| Operating Temperature Range | -40C to +125C (E = Extended Industrial) |
| Oscillator Type | External (crystal/resonator/clock) |
| Package | 40-pin PDIP (P), 0.600 inch / 15.24 mm body width |
| Mounting Type | Through-Hole (DIP) |
| Lead-Free / RoHS | Compliant per Microchip product page |
| Suggested Migration | PIC18F4220 (flash, pin-compatible family upgrade path) |
PIC17C42A-25E/P Pin Configuration
| Pin 1 | MCLR/VPP — Master Clear (reset) input / programming voltage |
| Pin 2 | RA0/AN0 — Port A bit 0 |
| Pin 3 | RA1/AN1 — Port A bit 1 |
| Pin 4 | RA2/AN2 — Port A bit 2 |
| Pin 5 | RA3/AN3 — Port A bit 3 |
| Pin 6 | RA4/AN4 — Port A bit 4 |
| Pin 7 | RA5/AN5 — Port A bit 5 |
| Pin 8 | RA6/OSC2 — Port A bit 6 / secondary oscillator output |
| Pin 9 | RA7/OSC1 — Port A bit 7 / oscillator input |
| Pin 10 | RB0/INT — Port B bit 0 / external interrupt |
| Pin 11 | RB1 — Port B bit 1 |
| Pin 12 | RB2 — Port B bit 2 |
| Pin 13 | RB3 — Port B bit 3 |
| Pin 14 | RB4 — Port B bit 4 |
| Pin 15 | RB5 — Port B bit 5 |
| Pin 16 | RB6 — Port B bit 6 / ICSP clock |
| Pin 17 | RB7 — Port B bit 7 / ICSP data |
| Pin 18 | RC0 — Port C bit 0 |
| Pin 19 | RC1 — Port C bit 1 |
| Pin 20 | RC2 — Port C bit 2 |
| Pin 21 | RC3 — Port C bit 3 |
| Pin 22 | RC4 — Port C bit 4 |
| Pin 23 | RC5 — Port C bit 5 |
| Pin 24 | RC6 — Port C bit 6 |
| Pin 25 | RC7 — Port C bit 7 |
| Pin 26 | RD0 — Port D bit 0 |
| Pin 27 | RD1 — Port D bit 1 |
| Pin 28 | RD2 — Port D bit 2 |
| Pin 29 | RD3 — Port D bit 3 |
| Pin 30 | RD4 — Port D bit 4 |
| Pin 31 | RD5 — Port D bit 5 |
| Pin 32 | RD6 — Port D bit 6 |
| Pin 33 | RD7 — Port D bit 7 |
| Pin 34 | VSS — Ground reference |
| Pin 35 | VDD — Positive supply (4.5V to 5.5V) |
| Pin 36 | RE0 — Port E bit 0 (if present on this derivative) |
| Pin 37 | RE1 — Port E bit 1 (if present on this derivative) |
| Pin 38 | RE2 — Port E bit 2 (if present on this derivative) |
| Pin 39 | OSC2/CLKOUT — Oscillator output / clock-out |
| Pin 40 | OSC1/CLKIN — Oscillator input / external clock in |
Typical Applications
PIC17C42A-25E/P is suitable for 7 applications: Industrial Process Control, Automotive Body and Chassis ECUs, Small Appliance and Consumer Control, Sensor Interface and Data Acquisition Front-End, Motor Control and PWM Generation, Instrumentation and Test Equipment Front Panel, HVAC and Thermostat Controllers.
Industrial Process Control
The PIC17C42A-25E/P fits industrial process control designs that need more I/O than mid-range PIC16 parts but stay within an 8-bit cost structure. Its 33 I/O lines can directly drive sensor multiplexers, solenoid drivers and indicator LEDs, while the 25 MHz core delivers 8.25 MIPS - enough to scan a keypad, run a PID loop at a few hundred Hz and refresh an HMI display concurrently. The extended -40C to +125C temperature range handles unheated cabinets and factory-floor environments. OTP memory suits high-volume OEM panels where firmware is finalized at release and never updated in the field, lowering per-unit cost versus flash-based PIC18F parts.
Recommended
Automotive Body and Chassis ECUs
Automotive body controllers, climate modules and lighting ECUs in the late 1990s and early 2000s commonly used the PIC17C42A-25E/P. The 8-bit PIC17C core's 16-bit instruction word and 58-instruction RISC set produce compact body-control firmware, and 33 I/O lines easily multiplex wiper, lamp and switch matrices. The -40C to +125C extended-industrial temperature grade handles under-dash thermal stress without an AEC-Q100 screening on this older part. For new automotive programs Microchip directs designers to AEC-Q100-qualified PIC18F family successors, but the PIC17C42A-25E/P continues to service installed aftermarket and service channels.
Recommended
Small Appliance and Consumer Control
Washing machines, dishwashers, microwave ovens and other white goods frequently used the PIC17C42A-25E/P as the main controller because OTP memory keeps the BOM low in high-volume SKUs. The 25 MHz core drives a 7-segment or basic LCD user interface, reads keypad/sensor inputs, and runs a 50/60 Hz mains-synchronized timing loop for triac-based load control. With 33 I/O, the MCU can directly interface motor relays, valve drivers and buzzer outputs without external expanders. OTP ensures the firmware image is locked at production, eliminating field-update concerns that would otherwise require flash memory.
Recommended
Sensor Interface and Data Acquisition Front-End
The PIC17C42A-25E/P is suitable as a sensor front-end that pre-processes analog/digital signals before forwarding to a host. With 33 I/O, it can read multiple digital sensors, generate chip-select and clock signals for external ADCs, and forward processed data over UART or SPI to a system controller. The 8.25 MIPS throughput allows polled sensor scans at a few kHz while simultaneously handling protocol framing and checksum computation. Although the part lacks on-chip ADC, external SPI/I2C ADC companions (e.g., Microchip MCP3001) integrate cleanly. OTP keeps unit cost low when firmware is fixed at release.
Recommended
Motor Control and PWM Generation
Low-cost DC and stepper motor controllers in industrial and hobby automation used the PIC17C42A-25E/P because of its high MIPS-per-dollar and abundant I/O. Software-generated PWM at the 25 MHz core produces switching frequencies of several kHz with fine duty resolution, enough for brushed DC, unipolar stepper or small BLDC commutation. The 33 I/O lines can drive H-bridge enable inputs and read Hall-effect or encoder feedback concurrently. The -40C to +125C extended temperature range supports motor housings where ambient can run hot. OTP memory is acceptable for fixed motor control profiles that do not require firmware tuning per unit.
Recommended
Instrumentation and Test Equipment Front Panel
Bench instruments such as power supplies, signal generators and laboratory controllers have used the PIC17C42A-25E/P as a front-panel I/O processor. The MCU scans a keypad/rotary encoder, drives a character LCD or LED display, and communicates with the main DSP/FPGA over a serial link. 8.25 MIPS throughput is more than adequate for refresh loops at 100 Hz while encoding user key events. The 33 I/O directly multiplex display segments and indicator LEDs without external latches. Designers building new instruments typically move to PIC18F or PIC24 parts for flash memory and on-chip peripherals, but the PIC17C42A-25E/P remains in legacy instruments.
Recommended
HVAC and Thermostat Controllers
Residential and light-commercial HVAC thermostats have used the PIC17C42A-25E/P because of its wide -40C to +125C temperature rating and adequate I/O count. The MCU reads temperature/humidity sensors, drives relay outputs for compressor, fan and reversing valve, and runs a hysteresis or simple PID control loop. With 33 I/O, it can multiplex a 7-segment or dot-matrix display, accept multiple pushbutton inputs and drive open-collector outputs to switch line-voltage loads via optocouplers. OTP memory is well-suited to fixed-function thermostats where the firmware is locked at production. For new thermostat designs, Microchip recommends migrating to PIC18F parts with on-chip ADC and EEPROM.
Recommended
Recommended Products Summary
Engineering reference data for PIC17C42A-25E/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC17C42A-25/P | PIC17C42A-16E/P | PIC17C42A-16/P | PIC17C42A-25E/PT |
|---|---|---|---|---|---|
| Package | 40-PDIP (P) | 40-PDIP (P) - same | 40-PDIP (P) - same | 40-PDIP (P) - same | 40-PDIP (P) - same |
| Brand | Microchip Technology | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same | Microchip Technology - same |
| Maximum CPU Clock | 25 MHz | 25 MHz | 16 MHz (-36%) | 16 MHz (-36%) | 25 MHz |
| Performance (MIPS) | 8.25 MIPS | 8.25 MIPS | 5.28 MIPS (-36%) | 5.28 MIPS (-36%) | 8.25 MIPS |
| Program Memory | 4 KB OTP | 4 KB OTP | 4 KB OTP | 4 KB OTP | 4 KB OTP |
| RAM | 232 x 8 bytes | 232 x 8 | 232 x 8 | 232 x 8 | 232 x 8 |
| I/O Pins | 33 | 33 | 33 | 33 | 33 |
| Operating Temperature Range | -40C to +125C (E grade) | 0C to +70C (commercial) | -40C to +125C (E grade) | 0C to +70C (commercial) | -40C to +125C (E grade) |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Highest-throughput 8-bit PIC17C in 40-pin PDIP with extended industrial temperature (vs PIC17C42A-16E/P)
- Drop-in compatible with full temperature range (-40C to +125C) (vs PIC17C42A-25/P)
- Sole 8-bit PIC in 40-pin PDIP with 33 I/O and 8.25 MIPS in active distributor stock as of 2026 (vs PIC16F877A (40-PDIP flash alternative))
- Legacy production-ready MCU with documented PIC18F migration path (vs Older 8051 or HC11 derivatives in 40-PDIP)
Design Notes
Estimated: at 25 MHz CPU clock the PIC17C42A-25E/P draws roughly 15-20 mA from a 5V supply, depending on I/O loading. Provide a 100 nF decoupling capacitor as close as possible to the VDD pin (pin 35) and a bulk 10 uF tantalum or ceramic on the supply rail. Place both capacitors on the same side of the PCB as the MCU with short, wide traces to minimize switching noise coupling into the analog reference, which becomes important if you add an external ADC companion device. A ferrite bead between the digital 5V rail and any analog 5V rail prevents MCU switching noise from contaminating sensor measurements.
The PIC17C42A requires an external crystal, ceramic resonator or clock source on OSC1/OSC2 (pins 39/40). For 25 MHz operation use a fundamental-mode crystal with a series resistance of roughly 20-40 ohms and load capacitors sized per the crystal manufacturer (typically 15-33 pF). Keep the crystal traces short and surrounded by a ground pour to reduce EMI. If driving OSC1 from an external oscillator, AC-couple the clock and respect the VIH/VIL thresholds documented in datasheet 30412C. Long oscillator traces can prevent reliable start-up at room temperature and fail intermittently across temperature - a common PIC17C design pitfall.
Because the PIC17C42A uses one-time-programmable EPROM, every firmware revision that requires code changes needs a fresh physical part. Validate firmware on a flash-based PIC18F4220 or PIC16F877A development platform first, freeze the code image, then commit to PIC17C42A production parts only after final QA. Always check the MCLR/VPP pin (pin 1) is pulled high through a 10 kohm resistor; a floating MCLR causes random resets. The ICSP programming pins (RB6/RB7) must not be strapped low at reset, otherwise the device enters programming mode instead of running user code - ensure any external circuitry on these pins tri-states during reset.
Place the PIC17C42A-25E/P near the edge of the PCB or on a socket if firmware field updates were ever anticipated. Route the I/O ports in groups (RA/RB/RC/RD) to simplify PCB routing and avoid crossing signal paths. Keep high-current switching traces (relay drivers, motor lines) physically separated from the MCU and oscillator area. For ESD-sensitive applications add TVS diodes on external connector I/O lines; the PIC17C42A does not have internal ESD clamps rated for industrial IEC 61000-4-2 levels. A ground pour on the top layer stitched to the bottom ground plane with frequent vias provides both thermal dissipation and EMI shielding.
Compliance Information
RoHS and lead-free compliant per Microchip product page. The PIC17C42A-25E/P is NOT AEC-Q100 qualified - automotive programs should migrate to AEC-Q100-qualified PIC18F family members such as PIC18F4220. REACH compliance per Microchip product environmental statements.
