PIC17C42AT-33/PT - 8-bit 33MHz 4KB OTP MCU | Microchip | TQFP-44
MPN: PIC17C42AT-33/PT ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.5 | $12.50 |
| 10 | $11.25 | $112.50 |
| 100 | $10 | $1,000.00 |
| 500 | $8.75 | $4,375.00 |
| 1,000 | $7.5 | $7,500.00 |
PIC17C42AT-33/PT Overview
An 8-bit microcontroller is a single-chip computer built around an 8-bit data path, on-chip program memory, RAM, and peripherals. MCUs sit within the broader taxonomy of microprocessors -> microcontrollers -> embedded controllers -> semiconductor ICs. Within Microchip's portfolio, the PIC17C family bridges PIC16 mid-range parts and the later PIC18 enhanced family, offering higher clock rates and I/O counts for embedded control tasks.
Key features include 33 MHz maximum clock, 4 KB OTP program memory, 232 bytes data RAM, 33 I/O pins, and 4-channel 8-bit analog-to-digital conversion capability typical of the family. The '33' suffix denotes the maximum clock speed, the 'A' indicates an OTP revision, and the 'T' marks tape-and-reel packaging. The TQFP-44 (10x10 mm) package exposes four 8-bit I/O ports plus dedicated oscillator, reset, interrupt, and ADC reference pins.
The PIC17C42A core uses a Harvard architecture with separate program and data buses, an 8-level deep hardware stack, and a 4-cycle instruction clock. The 16-bit-wide OTP program memory allows single-cycle instruction fetches at the rated clock, supporting deterministic interrupt response for real-time control loops.
Typical applications include industrial control logic, appliance motor control, automotive body controllers, security and access systems, and legacy embedded products designed in the mid-1990s. The PIC17C42A's 33 I/O lines comfortably drive keypad scanning, LED multiplexing, and parallel sensor interfaces without external glue logic.
When designing with this part, note that OTP memory cannot be re-programmed in-circuit; firmware must be verified externally before commitment. The 5V supply and TTL-level I/O simplify interface to legacy CMOS peripherals but require level shifting for modern 3.3V devices.
This page synthesizes distributor stock, drop-in compatible PIC17C family alternatives, and design notes that go beyond the manufacturer datasheet summary, helping engineers source and qualify parts faster.
Drop-in alternatives for PIC17C42AT-33/PT — 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-33/PT (same form factor and footprint) — differing in Program Memory Type, Core Architecture, Package, Program Memory Size, Maximum Clock Frequency.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC17C42A-33/PT
✅ Drop-In✓ In Stock
$9.65 / Unit
View Datasheet →PIC17C42AT-33I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC17C42AT-25/PT
✅ Drop-In✓ In Stock
$10.5 / Unit
View Datasheet →PIC17C42A-33I/P
✅ Drop-In✓ In Stock
$6.2 / Unit
View Datasheet →PIC17C42A-25/PT
✅ Drop-In✓ In Stock
$5.55 / Unit
View Datasheet →PIC17C42AT-33/PT Maximum Ratings & Electrical Characteristics
| Architecture | 8-bit Harvard RISC |
| Family | PIC17C4x |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Program Memory Size | 4 KB |
| Data RAM | 232 bytes |
| Maximum Clock Frequency | 33 MHz |
| I/O Pins | 33 |
| Instruction Word Width | 16 bits |
| Hardware Stack Depth | 8 levels |
| Package | TQFP-44 (PT) 10x10 mm |
| Mounting Type | Surface Mount |
PIC17C42AT-33/PT 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/TOCKI — PORTA bit 4 / Timer0 clock input |
| Pin 6 | RA5 — PORTA bit 5 |
| Pin 7 | RA6 — PORTA bit 6 |
| Pin 8 | RA7 — PORTA bit 7 |
| Pin 9 | RB0/INT — PORTB bit 0 / external interrupt |
| Pin 10 | RB1 — PORTB bit 1 |
| Pin 11 | RB2 — PORTB bit 2 |
| Pin 12 | RB3 — PORTB bit 3 |
| Pin 13 | RB4 — PORTB bit 4 |
| Pin 14 | RB5 — PORTB bit 5 |
| Pin 15 | RB6 — PORTB bit 6 |
| Pin 16 | RB7 — PORTB bit 7 |
| Pin 17 | RC0 — PORTC bit 0 |
| Pin 18 | RC1 — PORTC bit 1 |
| Pin 19 | RC2 — PORTC bit 2 |
| Pin 20 | RC3 — PORTC bit 3 |
| Pin 21 | RC4 — PORTC bit 4 |
| Pin 22 | RC5 — PORTC bit 5 |
| Pin 23 | RC6 — PORTC bit 6 |
| Pin 24 | RC7 — PORTC bit 7 |
| Pin 25 | RD0 — PORTD bit 0 |
| Pin 26 | RD1 — PORTD bit 1 |
| Pin 27 | RD2 — PORTD bit 2 |
| Pin 28 | RD3 — PORTD bit 3 |
| Pin 29 | RD4 — PORTD bit 4 |
| Pin 30 | RD5 — PORTD bit 5 |
| Pin 31 | RD6 — PORTD bit 6 |
| Pin 32 | RD7 — PORTD bit 7 |
| Pin 33 | RE0 — PORTE bit 0 |
| Pin 34 | RE1 — PORTE bit 1 |
| Pin 35 | RE2 — PORTE bit 2 |
| Pin 36 | OSC1 — Oscillator input |
| Pin 37 | OSC2 — Oscillator output |
| Pin 38 | MCLR — Master clear reset |
| Pin 39 | Vss — Ground |
| Pin 40 | Vdd — Positive supply |
| Pin 41 | AVss — Analog ground |
| Pin 42 | AVdd — Analog positive supply |
| Pin 43 | Vref — ADC voltage reference |
| Pin 44 | NC — Not connected (per datasheet) |
Typical Applications
PIC17C42AT-33/PT is suitable for 6 applications: Industrial Control Logic, Appliance Motor Control, Automotive Body Controllers, Security and Access Control Systems, Legacy Embedded Instrumentation, Point-of-Sale Terminal Controllers.
Industrial Control Logic
The PIC17C42AT-33/PT's 33 MHz clock (8.25 MIPS) and 33 I/O pins make it well-suited for industrial control logic boards that scan keypads, multiplex LEDs, and drive relays in factory automation. Its Harvard architecture delivers deterministic interrupt response for time-critical control loops, and the 4 KB OTP program memory holds substantial state-machine firmware. At 33 MHz, the device can service multiple high-speed sensors and PWM outputs in parallel.
Recommended
Appliance Motor Control
The PIC17C42AT-33/PT drives appliance motor controllers including washing machines, dishwashers, and HVAC blowers. Its 33 MHz clock supports real-time back-EMF sampling and zero-cross detection for triac-based speed control, while 33 I/O lines interface to user panels, sensors, and power switches. The OTP program memory ensures firmware integrity in mass-produced appliances where field re-programming is not required.
Recommended
Automotive Body Controllers
Although superseded in new automotive designs, the PIC17C42AT-33/PT was widely deployed in 1990s-era body controllers for window lifts, mirror adjustment, and seat control modules. Its 33 I/O lines handle multiple motor drivers and switch inputs, while the 33 MHz CPU executes CAN or LIN protocol stacks with sufficient timing margin. Modern automotive designs favor AEC-Q100 qualified parts, but many legacy modules still rely on PIC17C42A silicon.
Recommended
Security and Access Control Systems
The PIC17C42AT-33/PT powers security panels, keypads, and RFID access controllers where its 33 MHz clock supports real-time encryption and RFID baseband decoding. The 4 KB OTP memory stores credential databases and access schedules, and the 33 I/O lines interface to keypads, displays, door strikes, and alarm outputs. OTP memory prevents post-deployment tampering, a security advantage over flash-based MCUs.
Recommended
Legacy Embedded Instrumentation
Test and measurement instruments designed in the mid-1990s often used the PIC17C42AT-33/PT for front-panel control, ADC sequencing, and GPIB or RS-232 host interfaces. Its 33 MHz clock supports GPIB handshake timing and ADC burst sampling, while 33 I/O lines drive LCD displays, keypads, and relay multiplexers. Maintaining these legacy instruments requires PIC17C42A family knowledge and ongoing component sourcing.
Recommended
Point-of-Sale Terminal Controllers
The PIC17C42AT-33/PT served in legacy point-of-sale terminals for receipt printer control, magnetic stripe reader handling, and keypad scanning. Its 33 I/O lines drive printer stepper motors, scan switches, and serial ports to host cash registers, while the 4 KB OTP stores terminal ID and encryption keys. Modern POS systems have migrated to ARM Cortex-M, but legacy units still require PIC17C42A service parts.
Recommended
Recommended Products Summary
Engineering reference data for PIC17C42AT-33/PT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC17C42A-33/PT | PIC17C42AT-33I/PT | PIC17C42AT-25/PT | PIC17C42A-33I/P | PIC17C42A-25/PT |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | TQFP-44 (PT) | TQFP-44 (PT) - same | TQFP-44 (PT) - same | TQFP-44 (PT) - same | TQFP-44 (PT) - same | TQFP-44 (PT) - same |
| Maximum Clock Frequency | 33 MHz | 33 MHz | 33 MHz | 25 MHz | 33 MHz | 25 MHz |
| Program Memory | 4 KB OTP | 4 KB OTP | 4 KB OTP | 4 KB OTP | 4 KB OTP | 4 KB OTP |
| Data RAM | 232 bytes | 232 bytes | 232 bytes | 232 bytes | 232 bytes | 232 bytes |
| I/O Pins | 33 | 33 | 33 | 33 | 33 | 33 |
| Temperature Grade | Commercial (0C to +70C) | Commercial | Industrial (-40C to +85C) | Commercial | Industrial (-40C to +85C) | Commercial |
| Packaging Form | Tape & Reel | Tray | Tape & Reel | Tape & Reel | Tray | Tray |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Tape-and-reel packaging for high-volume SMT assembly (vs PIC17C42A-33/PT)
- Higher maximum clock speed than 25 MHz variants (vs PIC17C42AT-25/PT)
- Legacy-compatible instruction set for existing firmware (vs Modern PIC18F or PIC16F parts)
Design Notes
The PIC17C42AT-33/PT uses One-Time Programmable (OTP) EPROM that cannot be electrically erased. Use UV-erasing windowed parts (ceramic package) for firmware development, and verify firmware with the full production test suite before committing to plastic OTP. A single programming mistake will scrap the entire batch.
The PIC17C42AT-33/PT requires a clean 5V supply with decoupling: 100 nF ceramic capacitor within 5 mm of Vdd and a bulk 10 uF tantalum or ceramic on the supply rail. The analog AVdd pin should be bypassed separately from digital Vdd to prevent ADC noise coupling. Power-on ramp should meet the datasheet's minimum Vdd rise time for proper reset.
Route the 33 MHz oscillator traces (OSC1/OSC2) with short, symmetrical paths and guard them with a ground plane pour to prevent EMI coupling into adjacent I/O lines. Place the MCLR pull-up resistor within 25 mm of the pin and add a 100 nF decoupling cap on MCLR to suppress noise-induced resets in noisy industrial environments.
Compliance Information
Compliance data not present in verified web data; PIC17C4x family predates widespread RoHS reporting. AEC-Q100 not applicable - this is an obsolete commercial/industrial MCU, not automotive-qualified. Engineers should request compliance documentation directly from authorized distributors for new production.
