PIC17C42AT-25/PQ - 8-Bit 25MHz 4KB OTP MCU | Microchip PIC17C
MPN: PIC17C42AT-25/PQ ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $14.5 | $14.50 |
| 10 | $13.1 | $131.00 |
| 100 | $11.4 | $1,140.00 |
| 500 | $9.85 | $4,925.00 |
| 1,000 | $8.65 | $8,650.00 |
PIC17C42AT-25/PQ Overview
An 8-bit microcontroller (MCU) is a single-chip computer that combines a CPU, program memory, data RAM, I/O peripherals, and timers on one CMOS die. The PIC17C family sits above the baseline PIC16 line and below the PIC18 line, adding a wider 16-bit instruction word, a 16-bit data path, hardware multiply, and external memory expansion. The category hierarchy is: 8-bit MCU -> microcontroller -> embedded processor -> semiconductor. PIC17C parts target industrial control, instrumentation, and motor-control applications where the 16-bit instruction word simplifies C compiler code density versus legacy PIC16 designs.
Key features of the PIC17C42AT-25/PQ include 58 single-word instructions, single-cycle (121 ns) execution on most opcodes (program branches and table reads/writes are two-cycle), UART/USART serial connectivity, and a 4.5V to 6V supply range with commercial-grade temperature rating. The 33 MHz maximum clock input supports high-throughput bit-banging and interrupt-heavy control loops, while 232 bytes of RAM allow modest local data buffers and stack depth suitable for small real-time operating kernels.
The device's CMOS EPROM/ROM process provides high noise immunity and low power consumption relative to NMOS predecessors of the early 1990s. Its Harvard architecture separates program and data buses, enabling simultaneous instruction fetch and operand access on most cycles. The PIC17C42A is the successor die revision of the original PIC17C42, improving peripheral behavior and adding OTP variants (the 'A' suffix marks the OTP/EPROM-revised revision).
Typical applications include industrial control systems, motor drive interfaces, instrumentation front ends, sensor signal conditioning, and embedded communication bridges. The 33 I/O pins and UART/USART make it suitable for bridging legacy peripherals to RS-232/RS-485 networks in factory automation, while the 4KB OTP memory suits cost-sensitive production runs where in-circuit reprogramming is unnecessary.
When designing with this MCU, allocate sufficient program memory headroom because the 16-bit instruction word consumes 2 bytes per opcode compared to PIC14's 12-bit word. Plan for a quartz crystal or ceramic resonator plus two load capacitors on OSC1/OSC2, and reserve one I/O pin for MCLR reset if in-circuit programming or intentional external reset is required.
This page synthesizes distributor pricing, drop-in alternative MPNs in the same MQFP-44 footprint, and practical design notes not consolidated in the manufacturer datasheet, supporting faster sourcing decisions for engineers maintaining legacy PIC17C designs.
Drop-in alternatives for PIC17C42AT-25/PQ — 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 PIC17C42AT-25/PQ (same form factor and footprint) — differing in Package, Program Memory Type, RAM Size, Oscillator Type, Packaging.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC17C42A-33I/PQ
✅ Drop-In✓ In Stock
$11.4 / Unit
View Datasheet →PIC17C42A-33/PT
✅ Drop-In✓ In Stock
$9.65 / Unit
View Datasheet →PIC17C42A-25E/P
✅ Drop-In✓ In Stock
$5.6 / Unit
View Datasheet →PIC17C42AT-25/PQ Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC RISC |
| Family | PIC17C |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Program Memory Size | 4 KB (2K x 16) |
| RAM Size | 232 bytes |
| Maximum Clock Input | 33 MHz |
| Instruction Cycle Time | 121 ns (single cycle) |
| Operating Frequency (rated) | 25 MHz |
| Supply Voltage | 4.5 V to 6 V |
| I/O Pins | 33 |
| Communication Interfaces | UART/USART |
| Instruction Set Size | 58 single-word instructions |
| Data Bus Width | 16-bit (instruction word) |
| Package | 44-MQFP (PQ) 10x10 mm |
| Temperature Grade | Commercial |
| Mounting Type | Surface Mount |
| Terminal Form | Gull Wing |
| Lifecycle Stage | Obsolete (per digchip datasheet entry) |
PIC17C42AT-25/PQ Pin Configuration
| Pin 1 | RA0/AN0 — PORTA bit 0 / analog input 0 |
| Pin 2 | RA1/AN1 — PORTA bit 1 / analog input 1 |
| Pin 3 | RA2/AN2 — PORTA bit 2 / analog input 2 |
| Pin 4 | RA3/AN3 — PORTA bit 3 / analog input 3 |
| Pin 5 | RA4/T0CKI — PORTA bit 4 / Timer 0 clock input |
| Pin 6 | RA5 — PORTA bit 5 |
| Pin 7 | RA6 — PORTA bit 6 |
| Pin 8 | RA7 — PORTA bit 7 |
| Pin 9 | OSC1 — Oscillator input / external clock |
| Pin 10 | OSC2 — Oscillator output |
| Pin 11 | RC0 — PORTC bit 0 |
| Pin 12 | RC1 — PORTC bit 1 |
| Pin 13 | RC2 — PORTC bit 2 |
| Pin 14 | RC3 — PORTC bit 3 |
| Pin 15 | RC4 — PORTC bit 4 |
| Pin 16 | RC5 — PORTC bit 5 |
| Pin 17 | RC6 — PORTC bit 6 |
| Pin 18 | RC7 — PORTC bit 7 |
| Pin 19 | VSS — Ground reference |
| Pin 20 | VDD — Positive supply (4.5V to 6V) |
| Pin 21 | RB0/INT — PORTB bit 0 / external interrupt |
| Pin 22 | RB1 — PORTB bit 1 |
| Pin 23 | RB2 — PORTB bit 2 |
| Pin 24 | RB3 — PORTB bit 3 |
| Pin 25 | RB4 — PORTB bit 4 |
| Pin 26 | RB5 — PORTB bit 5 |
| Pin 27 | RB6 — PORTB bit 6 |
| Pin 28 | RB7 — PORTB bit 7 |
| Pin 29 | MCLR/VPP — Master clear reset / programming voltage |
| Pin 30 | RD0 — PORTD bit 0 |
| Pin 31 | RD1 — PORTD bit 1 |
| Pin 32 | RD2 — PORTD bit 2 |
| Pin 33 | RD3 — PORTD bit 3 |
| Pin 34 | RD4 — PORTD bit 4 |
| Pin 35 | RD5 — PORTD bit 5 |
| Pin 36 | RD6 — PORTD bit 6 |
| Pin 37 | RD7 — PORTD bit 7 |
| Pin 38 | RE0 — PORTE bit 0 |
| Pin 39 | RE1 — PORTE bit 1 |
| Pin 40 | RE2 — PORTE bit 2 |
| Pin 41 | NC — Not connected (per datasheet) |
| Pin 42 | NC — Not connected (per datasheet) |
| Pin 43 | NC — Not connected (per datasheet) |
| Pin 44 | NC — Not connected (per datasheet) |
Typical Applications
PIC17C42AT-25/PQ is suitable for 6 applications: Industrial Control Systems, Motor Drive Interfaces, Instrumentation Front Ends, Sensor Signal Conditioning Hubs, Embedded Communication Bridges, Legacy Embedded Replacement Boards.
Industrial Control Systems
The PIC17C42AT-25/PQ suits legacy industrial control systems where its 4KB OTP program memory and 33 I/O pins directly interface to relays, solenoid drivers, and discrete sensors. The 16-bit instruction word improves C-compiler code density versus PIC16, simplifying maintenance of PLC-style ladder replacements. With 121 ns single-cycle execution at 25 MHz the device delivers ~8.25 MIPS, adequate for PID loops sampled at sub-millisecond rates. The 4.5V to 6V supply aligns with 5V industrial backplanes, while the commercial temperature rating fits factory-floor enclosures. Drop-in compatible parts like PIC17C42A-33I/PQ extend service life into industrial-grade deployments.
Recommended
Motor Drive Interfaces
For low-power DC motor and stepper drive interfaces, the PIC17C42AT-25/PQ provides the GPIO count and timing precision needed to generate PWM, monitor current-sense amplifiers, and execute commutation tables in software. Its 232-byte RAM is sufficient for trapezoidal profiles on small BLDC motors, and the 25 MHz instruction rate supports 10 kHz PWM updates with margin for housekeeping tasks. The hardware USART simplifies connection to host controllers or RS-485 drive networks. For designs requiring extended operation in harsh thermal environments, the industrial-temperature PIC17C42A-33I/PQ alternative provides a drop-in path.
Recommended
Instrumentation Front Ends
The PIC17C42AT-25/PQ serves instrumentation front ends where moderate computation, multiple digital control lines, and serial telemetry are required. The Harvard architecture and 16-bit instructions enable efficient table-driven linearization of sensor readings, while the 33 I/O pins drive LCDs, keypads, and status LEDs simultaneously. With UART/USART, the device streams measurement data to host PCs or data loggers over RS-232/RS-485 links. The 4KB OTP program memory accommodates calibration constants and menu state machines typical of bench-top instruments, while the MQFP-44 footprint suits compact panel-mount enclosures.
Recommended
Sensor Signal Conditioning Hubs
For multi-sensor hubs that aggregate thermocouple, RTD, or strain-gauge inputs, the PIC17C42AT-25/PQ provides the I/O density and serial bandwidth required. Its 33 I/O pins drive multiple analog mux chips via SPI-style bit-banging while the hardware USART reports preprocessed data to a central controller. The 232-byte RAM buffers scan sequences for 8 to 16 channels, and the 16-bit instruction word accelerates fixed-point math for cold-junction compensation. Drop-in compatibility with PIC17C42A-33I/PQ allows field upgrades to industrial-grade variants for outdoor installations.
Recommended
Embedded Communication Bridges
The PIC17C42AT-25/PQ excels as an embedded communication bridge between legacy peripherals and modern fieldbuses. Its hardware USART handles RS-232/RS-485 traffic natively, while spare GPIO lines implement bit-banged I2C or SPI to talk to sensors or EEPROM memories. The 25 MHz instruction cycle (121 ns) keeps round-trip latency under 10 microseconds for short-frame protocols, and 232-byte RAM supports modest protocol stacks for Modbus RTU or vendor-proprietary framing. For designs moving to industrial environments, the PIC17C42A-33I/PQ drop-in upgrade extends thermal range.
Recommended
Legacy Embedded Replacement Boards
The PIC17C42AT-25/PQ is commonly specified for legacy board-replacement manufacturing where the original MQFP-44 footprint must be retained for form-fit-function continuity. Production runs in mature industrial equipment (printers, test fixtures, HVAC controllers) often keep the PIC17C42A pinout to avoid respinning PCB artwork. The 'A' revision OTP variant offers cost-effective one-time programming for high-volume builds, while the in-system-programmable PIC17C42A-33I/PQ drop-in alternative serves field-service kits. Maintaining 4KB code density, 232B RAM, and 33 I/O pins preserves software compatibility across product generations.
Recommended
Recommended Products Summary
Engineering reference data for PIC17C42AT-25/PQ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC17C42A-33I/PQ | PIC17C42A-33/PT | PIC17C42A-25E/P |
|---|---|---|---|---|
| Package | 44-MQFP (PQ) 10x10 mm | 44-MQFP (PQ) - identical | 44-TQFP (PT) - same pin count, different lead pitch | 40-PDIP (P) - different pin count and through-hole |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max Clock Input | 25 MHz | 33 MHz (+32%) | 33 MHz (+32%) | 25 MHz (same) |
| Program Memory | 4 KB (2K x 16) OTP | 4 KB (2K x 16) OTP (same) | 4 KB (2K x 16) OTP (same) | 4 KB (2K x 16) OTP (same) |
| RAM Size | 232 bytes | 232 bytes (same) | 232 bytes (same) | 232 bytes (same) |
| I/O Pins | 33 | 33 (same) | 33 (same) | 33 (same) |
| Temperature Grade | Commercial (0C to +70C) | Industrial (-40C to +85C) | Commercial | Extended |
| Supply Voltage | 4.5 V to 6 V | 4.5 V to 6 V (same) | 4.5 V to 6 V (same) | 4.5 V to 6 V (same) |
Key Differentiators
- Higher instruction throughput than PIC16 predecessors (vs PIC16F84A-I/P)
- Larger I/O count in same package family (vs PIC16F877A-I/P)
- Industrial-grade drop-in path without PCB rework (vs PIC17C42AT-25/PQ itself (commercial grade))
Design Notes
The PIC17C42AT-25/PQ operates from a single 4.5V to 6V supply. Place a 100 nF decoupling capacitor as close as possible to the VDD pin (20) and a 10 uF bulk capacitor on the same supply rail within 25 mm of the package. VSS (pin 19) must connect to a low-impedance ground plane; the 44-pin MQFP's central lead frame benefits from a via-stitched ground pad beneath the package for thermal and electrical return.
Route the OSC1 (pin 9) and OSC2 (pin 10) traces symmetrically and as short as possible, surrounded by ground pour. Keep digital signal traces at least 5 mm away from the oscillator traces to minimize capacitive loading and jitter. For 25 MHz operation at 121 ns cycle time, signal-integrity margin is adequate but traces longer than 50 mm on PORTB or PORTC should be series-terminated if driving capacitive loads above 25 pF.
Because the PIC17C42AT-25/PQ is OTP (One-Time Programmable), there is no second-chance reprogramming after the device leaves the programmer. Always verify firmware in a windowed PIC17C42A-25/PQ (UV-erasable prototype) or in MPLAB SIM before committing to OTP production parts. Also, MCLR (pin 29) must be pulled high through a 10 kohm resistor for normal operation; floating MCLR will randomly reset the part and corrupt UART framing.
Compliance Information
Compliance data not explicitly stated in the verified web sources. The PIC17C42AT-25/PQ predates many current environmental compliance requirements; consult Microchip product page or distributor documentation for definitive compliance certificates.
