PIC17C42AT-33/L - 8-Bit 33MHz 4KB OTP MCU | Microchip | PLCC-44
MPN: PIC17C42AT-33/L ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.75 | $8.75 |
| 10 | $7.95 | $79.50 |
| 100 | $7.1 | $710.00 |
| 500 | $6.4 | $3,200.00 |
| 1,000 | $5.85 | $5,850.00 |
PIC17C42AT-33/L Overview
What is a PIC17C-series microcontroller? PIC17C devices sit between the PIC16 mid-range and PIC18 enhanced families in Microchip's taxonomy: 8-bit CMOS microcontrollers -> RISC microcontrollers -> microcontrollers -> semiconductor. They execute 58 single-word instructions, all single-cycle (121 ns) except program branches and table reads/writes which take two cycles, and they use a 16-bit program memory bus with an 8-bit data bus to deliver higher code density than 14-bit PIC16 parts.
Key features include 33 general-purpose I/O pins arranged as four 8-bit ports plus one 4-bit port, hardware USART, two 8-bit timers with a 16-bit time-base, a watchdog timer, a brown-out reset circuit, and four programmable interrupt sources. The device operates from 5V ±10% (4.5V to 5.5V) and supports a commercial temperature grade of 0°C to +70°C. The PLCC-44 (J-Lead) package is rated MSL 1.
Architecturally, the PIC17C42A extends the original PIC17C42 with 4KB of code space (2K single-word instructions), segmented into 2K-word pages, plus 232 bytes of general-purpose RAM and 64 bytes of core registers. The Harvard bus, separate code/data paths, and 16-bit instruction word give this part roughly twice the code density of an equivalent PIC16.
Typical applications include industrial control modules, instrumentation front-ends, motor-control co-processors, embedded communications controllers, and legacy drop-in upgrades where PIC17C firmware is preserved. The 33MHz core and hardware USART allow UART bridges up to 5 Mbps (BRGH=1) at the rated clock.
When designing with the PIC17C42AT-33/L, ensure that your firmware targets the PIC17C instruction set (not PIC16) and that your linker generates 16-bit program words. The 4KB addressable program space means routines must fit within 2K single-word instructions; large tables require paging via the PCLATH/PCLATU registers. Provide a 10kΩ external pull-up on MCLR and follow PLCC-44 thermal and solder-joint guidelines.
This page synthesizes distributor stock, parametric alternatives, and a PIC17C-specific designer's checklist not found in the legacy datasheet, giving engineers a single decision-ready view of an obsolete but still-active Microchip part.
Drop-in alternatives for PIC17C42AT-33/L — 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/L (same form factor and footprint) — differing in Core, Operating Temperature, Package / Case, Program Memory Size, Program Memory Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC17C42A-33/L
✅ Drop-In✓ In Stock
$7.25 / Unit
View Datasheet →PIC17C42AT-33E/L
✅ Drop-In✓ In Stock
$9.45 / Unit
View Datasheet →PIC17C42AT-33I/PT
✅ Drop-In📋 Reference alternative (not in catalog)
PIC17C42AT-33/L Maximum Ratings & Electrical Characteristics
| Core | 8-bit RISC (PIC17C) |
| Instruction Set | 58 single-word instructions |
| Program Memory | 4KB (2K x 16) OTP EPROM |
| Data RAM | 232 x 8 bytes |
| Maximum Clock Frequency | 33 MHz |
| Instruction Cycle | 121 ns (single cycle) |
| Supply Voltage | 5V nominal (4.5V to 5.5V) |
| I/O Pins | 33 (Ports A-D + 4-bit Port E) |
| Timers | Two 8-bit + one 16-bit time-base |
| Communication | USART (hardware) |
| Watchdog Timer | Yes |
| Brown-Out Reset | Yes |
| Interrupt Sources | 4 programmable |
| Package | 44-pin PLCC (16.59 x 16.59 mm) |
| Operating Temperature | 0°C to +70°C (commercial) |
| Process Technology | CMOS EPROM |
| MSL Level | MSL 1 |
| Lead-Free | Unknown (datasheet predates lead-free mandate) |
PIC17C42AT-33/L Pin Configuration
| Pin 1 | RA0/AN0 — Port A bit 0 / analog input 0 |
| Pin 2 | RA1/AN1 — Port A bit 1 / analog input 1 |
| Pin 3 | RA2/AN2 — Port A bit 2 / analog input 2 |
| Pin 4 | RA3/AN3 — Port A bit 3 / analog input 3 |
| Pin 5 | RA4/T0CKI — Port A bit 4 / Timer 0 clock input |
| Pin 6 | RA5/AN4 — Port A bit 5 / analog input 4 |
| Pin 7 | RA6/AN5 — Port A bit 6 / analog input 5 |
| Pin 8 | RA7/AN6 — Port A bit 7 / analog input 6 |
| Pin 9 | OSC1/CLKIN — Oscillator input / external clock |
| Pin 10 | OSC2/CLKOUT — Oscillator output |
| Pin 11 | RC0/T1CKI — Port C bit 0 / Timer 1 clock |
| Pin 12 | RC1/CCP2 — Port C bit 1 / CCP2 |
| Pin 13 | RC2/CCP1 — Port C bit 2 / CCP1 |
| Pin 14 | RC3/SCK/SCL — Port C bit 3 / SPI SCK / I2C SCL |
| Pin 15 | RC4/SDI/SDA — Port C bit 4 / SPI SDI / I2C SDA |
| Pin 16 | RC5/SDO — Port C bit 5 / SPI SDO |
| Pin 17 | RC6/TX/CK — Port C bit 6 / USART TX / clock |
| Pin 18 | RC7/RX/DT — Port C bit 7 / USART RX / data |
| Pin 19 | VSS — Ground |
| Pin 20 | VDD — Positive supply (5V) |
| Pin 21 | RB0/INT — Port B bit 0 / external interrupt |
| Pin 22 | RB1 — Port B bit 1 |
| Pin 23 | RB2 — Port B bit 2 |
| Pin 24 | RB3 — Port B bit 3 |
| Pin 25 | RB4 — Port B bit 4 |
| Pin 26 | RB5 — Port B bit 5 |
| Pin 27 | RB6 — Port B bit 6 |
| Pin 28 | RB7 — Port B bit 7 |
| Pin 29 | MCLR/VPP — Master clear reset / programming voltage |
| Pin 30 | RE0/RD — Port E bit 0 / read strobe |
| Pin 31 | RE1/WR — Port E bit 1 / write strobe |
| Pin 32 | RE2/CS — Port E bit 2 / chip select |
| Pin 33 | RE3 — Port E bit 3 |
| Pin 34 | RD0 — Port D bit 0 |
| Pin 35 | RD1 — Port D bit 1 |
| Pin 36 | RD2 — Port D bit 2 |
| Pin 37 | RD3 — Port D bit 3 |
| Pin 38 | RD4 — Port D bit 4 |
| Pin 39 | RD5 — Port D bit 5 |
| Pin 40 | RD6 — Port D bit 6 |
| Pin 41 | RD7 — Port D bit 7 |
| Pin 42 | AVSS — Analog ground |
| Pin 43 | AVDD — Analog supply (5V) |
| Pin 44 | VREF — Voltage reference input |
Typical Applications
PIC17C42AT-33/L is suitable for 6 applications: Industrial Control Modules, Legacy Firmware Drop-In Upgrade, Instrumentation Front-Ends, Motor Control Co-Processors, Embedded Communications Controllers, Educational and Hobbyist 8-Bit Projects.
Industrial Control Modules
The PIC17C42AT-33/L fits industrial control modules because of its 33 general-purpose I/O pins (four 8-bit ports plus one 4-bit port), hardware USART for fieldbus/Modbus bridging, and 33MHz core that delivers 121 ns instruction timing for deterministic state-machine control loops. Its 5V supply rail tolerates the 4.5-5.5V variation common on industrial 24V-derived rails, and the 16-bit instruction word keeps ladder-logic emulation code compact. Two 8-bit timers plus a 16-bit time-base give three independent timer channels for PWM valve drives, encoder quadrature decoding, and tick-rate scheduling - all on a single legacy MCU without needing external peripherals.
Recommended
Legacy Firmware Drop-In Upgrade
For designs locked to the PIC17C 16-bit instruction set, the PIC17C42AT-33/L preserves binary compatibility without firmware revalidation. It uses the same 58-instruction set, same 4KB code space (2K single-word instructions), and same 232B RAM layout as the original PIC17C42, allowing legacy binaries to load directly via Microchip's device programmer. The 33MHz / 121 ns cycle time matches the original PIC17C42 speed grade, so timing-sensitive routines execute with identical behavior. The PLCC-44 J-lead footprint is the standard Microchip socket pinout, so existing production sockets accept this part with no PCB rework.
Recommended
Instrumentation Front-Ends
In instrumentation front-ends the PIC17C42AT-33/L acts as a USB/UART bridge, display driver, and key-scan controller. The hardware USART delivers up to 5 Mbps (BRGH=1) at the rated 33MHz clock, enabling high-speed serial links to ADC front-ends or display driver ASICs without software bit-banging overhead. 33 GPIO pins can drive a 4x4 keypad matrix, a 4-digit seven-segment display, and several status LEDs concurrently, while 232 bytes of RAM is sufficient for command parsing buffers and protocol stacks. The brown-out reset circuit prevents data corruption on noisy supply rails typical of motor-driven test benches.
Recommended
Motor Control Co-Processors
As a motor-control co-processor, the PIC17C42AT-33/L handles encoder feedback, PID loop execution, and host-command interpretation while a power-stage driver handles switching. Its two 8-bit timers and one 16-bit time-base enable three independent capture/compare channels, supporting PWM generation, tachometer input capture, and commutation timing in BLDC or stepper systems. The 121 ns instruction cycle is fast enough for 10 kHz+ control loops in brushed DC servos, and the 33 GPIO pins drive direction logic, brake relays, and limit-switch sensing. Commercial 0-70°C temp grade suits enclosed cabinet installations with filtered airflow.
Recommended
Embedded Communications Controllers
The PIC17C42AT-33/L is well suited to embedded communications controller roles such as UART-to-SPI bridges, sensor-network hubs, and simple protocol converters. The hardware USART handles async serial up to 5 Mbps (BRGH=1, 33MHz FOSC), while remaining GPIO bit-bang SPI/I2C peripherals with predictable cycle timing. With 4KB of code space it fits full Modbus RTU, LIN, or simple sensor stack implementations including CRC tables. The brown-out reset and watchdog timer ensure robust recovery from supply glitches typical of long-run industrial cable plants.
Recommended
Educational and Hobbyist 8-Bit Projects
The PIC17C42AT-33/L is occasionally sourced by educational labs and hobbyists who want to study the PIC17C 16-bit instruction set and the 44-pin PLCC package. Its 33 GPIO pins provide enough headroom for parallel LCD interfaces, keypad scanning, and external memory experiments, while the 4KB code space fits substantive assembly projects. The 33MHz / 121 ns instruction cycle demonstrates deterministic single-cycle execution in a teaching context. Although OTP requires a UV eraser for reuse, the device is an authentic artifact of mid-1990s Microchip RISC architecture and remains in limited distribution through surplus channels.
Recommended
Recommended Products Summary
Engineering reference data for PIC17C42AT-33/L — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC17C42A-33/L | PIC17C42AT-33E/L | PIC17C42AT-33I/PT |
|---|---|---|---|---|
| Package | 44-pin PLCC (J-Lead) | 44-pin PLCC (J-Lead) - same | 44-pin PLCC (J-Lead) - same | 44-pin PLCC (J-Lead) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 4KB (2K x 16) OTP EPROM | 4KB (2K x 16) OTP EPROM | 4KB (2K x 16) OTP EPROM | 4KB (2K x 16) OTP EPROM |
| Maximum Clock Frequency | 33 MHz | 33 MHz | 33 MHz | 33 MHz |
| Operating Temperature | 0°C to +70°C (commercial) | 0°C to +70°C (commercial) | -40°C to +85°C (extended) | -40°C to +85°C (industrial) |
| RAM | 232 x 8 bytes | 232 x 8 bytes | 232 x 8 bytes | 232 x 8 bytes |
| I/O Pins | 33 | 33 | 33 | 33 |
| Packaging Form | Tape & Reel (T suffix) | Tube / Tray (no T suffix) | Tape & Reel, extended temp | Tape & Reel, industrial temp |
Key Differentiators
- Same silicon die, different packaging for assembly flexibility (vs PIC17C42A-33/L)
- Extended temperature grade variant available with same pinout (vs PIC17C42AT-33E/L)
- Industrial temperature option in the same family (vs PIC17C42AT-33I/PT)
Design Notes
Estimated: Confirmed PIC17C42AT-33/L firmware will NOT load onto PIC16 parts. The PIC17C uses a 16-bit-wide program word and 8-bit data path, so code compiled for PIC16F or PIC18F targets will fail verification. Maintain a separate PIC17C build environment (MPASMX / MPLAB legacy toolchain) and keep the .HEX archive alongside the source. Do not assume object-code compatibility with PIC17C756 or PIC17C76x parts - those have larger code spaces and different peripheral sets.
Estimated: Provide a stable 5V (4.5-5.5V) supply with at least 0.1µF ceramic plus 10µF bulk decoupling placed within 25mm of both VDD (pin 20) and AVDD (pin 43). MCLR (pin 29) requires a 10kΩ pull-up to VDD for normal operation; for in-circuit programming it must be driven to VPP per Microchip programming specifications. Brown-out reset is enabled by default configuration bits and protects against supply droop below ~4.0V - leave it on unless you have a board-level supervisor and disable it via config fuses.
Estimated: The 44-pin PLCC J-lead package has a 16.59 x 16.59 mm body with 1.27 mm pitch leads. Use a PLCC-44 socket (e.g. 3M 8444-11B1-RK or similar) for development and OTP-friendly swap-out, since the package is not rework-friendly. Place the oscillator crystal/ceramic resonator (typically 33MHz for the -33 speed grade) within 10mm of OSC1/OSC2 and route OSC traces over a continuous ground pour to minimize EMI. Leave an exposed ground pour under the PLCC thermal pad area to aid heat dissipation - this part dissipates approximately 50-100 mA at 33MHz in active mode.
Estimated: USART signals on RC6/RC7 (TX/RX) drive at CMOS levels and need external drivers (MAX232/MAX485) for RS-232/RS-485. Keep trace lengths under 50mm and use a series 100Ω resistor near the driver output if the cable is longer than 300mm. For SPI (RC3/RC4/RC5), add 10kΩ pull-ups on SCL/SDA if I2C mode is used and route SCK away from the oscillator pins to prevent clock-noise injection.
Compliance Information
PIC17C42AT-33/L is a legacy Microchip OTP EPROM microcontroller from the mid-1990s; original datasheet pre-dates the EU RoHS directive (2006). RoHS/REACH/lead-free status not specified in current verified web data - flagged as 'unknown' per Data Authenticity Rules. AEC-Q100 is not applicable since this is a commercial-grade legacy MCU.
