PIC17LC42A-08/L - 8MHz, 4KB EPROM 8-bit MCU | Microchip
MPN: PIC17LC42A-08/L ⚠ Last Time Buy| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.5 | $12.50 |
| 10 | $11.25 | $112.50 |
| 100 | $9.95 | $995.00 |
| 500 | $8.75 | $4,375.00 |
| 1,000 | $7.5 | $7,500.00 |
PIC17LC42A-08/L Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, memory (program + data), and peripherals onto one silicon die. The PIC17 family is one of Microchip's highest-performance 8-bit architectures, positioned as a stepping stone between baseline PIC16 devices and the newer PIC18/dsPIC families. It uses a RISC instruction set with only 58 single-word instructions to learn, a Harvard memory architecture, and a 16-bit instruction word width that yields higher code density than typical 8-bit MCUs.
Key features of the PIC17LC42A-08/L include four timers, two PWM modules, a watchdog timer for code-execution safety, a power-on reset (POR) circuit, and a USART for serial connectivity. The 'LC' suffix denotes the low-voltage CMOS variant supporting operation down to approximately 2.5 V, whereas the standard 'C' family operates at 4.5 V to 5.5 V. The device supports a 16-bit address bus width, allowing access to the full 64KB program memory map. Peripherals map onto a separate 16-bit data memory bus with 232 bytes of general-purpose RAM plus dedicated SFRs.
Typical applications for this MCU include industrial automation controllers, motor drive sequencers, HVAC control boards, and legacy embedded systems that were designed around the PIC17 architecture in the late 1990s. Its EPROM program memory allows in-circuit reprogramming via a UV-erasable windowed package, simplifying development cycles and small-batch production runs.
When designing with the PIC17LC42A-08/L, ensure your programmer supports the PIC17C4X device family. Decoupling capacitors (100 nF ceramic + 10 uF bulk) must be placed within 5 mm of VDD/VSS pins. Because this part is mature and primarily available through distributor stock, lead times may extend beyond those of newer PIC families; consider a PIC18F or dsPIC33 drop-in only after a full peripheral-mapping review.
Drop-in alternatives for PIC17LC42A-08/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 PIC17LC42A-08/L (same form factor and footprint) — differing in Maximum Clock Frequency, Program Memory Type, Core Architecture, Operating Temperature Range, Program Memory Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC17C42A-08/L
✅ Drop-In📋 Reference alternative (not in catalog)
PIC17LC42A-08I/L
✅ Drop-In📋 Reference alternative (not in catalog)
PIC17LC42A-08/P
✅ Drop-In✓ In Stock
$9.1 / Unit
View Datasheet →PIC17C42A-16E/P
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$5.85 / Unit
View Datasheet →PIC17C42A-25/PT
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$5.55 / Unit
View Datasheet →PIC17C42A-33I/P
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$6.2 / Unit
View Datasheet →PIC17LC42A-08/L Maximum Ratings & Electrical Characteristics
| Family | PIC17C4X |
| Core Architecture | 8-bit RISC |
| Maximum Clock Frequency | 8 MHz |
| Instruction Cycle Time | 121 ns (at 8 MHz clock) |
| Program Memory Type | EPROM (UV-erasable) |
| Program Memory Size | 4 KB (2K x 16) |
| Data RAM Size | 232 x 8 bytes |
| Number of I/O Pins | 33 |
| Number of Timers | 4 |
| PWM Modules | 2 |
| Watchdog Timer | Yes |
| Communication Interface | USART |
| Address Bus Width | 16-bit |
| Oscillator Type | External |
| Package / Case | 40-DIP (0.600, 15.24 mm) |
| Mounting Type | Through-Hole |
| Packaging | Tube |
| Instruction Set Size | 58 single-word instructions |
PIC17LC42A-08/L Pin Configuration
| Pin 1 | MCLR — Master Clear reset input |
| Pin 2 | RA0/AN0 — PORTA bit 0 / Analog input 0 |
| Pin 3 | RA1/AN1 — PORTA bit 1 / Analog input 1 |
| Pin 4 | RA2/AN2 — PORTA bit 2 / Analog input 2 |
| Pin 5 | RA3/AN3/VREF — PORTA bit 3 / Analog input 3 / Voltage reference |
| Pin 6 | RA4/T0CKI — PORTA bit 4 / Timer 0 clock input |
| Pin 7 | RA5/SS — PORTA bit 5 / Slave Select |
| Pin 8 | OSC1/CLKIN — Oscillator crystal input / external clock in |
| Pin 9 | OSC2/CLKOUT — Oscillator crystal output / clock out |
| Pin 10 | RC0/T1CKI — PORTC bit 0 / Timer 1 clock input |
| Pin 11 | RC1/CCP2 — PORTC bit 1 / CCP2 PWM output |
| Pin 12 | RC2/CCP1 — PORTC bit 2 / CCP1 PWM output |
| Pin 13 | RC3/SCK/SCL — PORTC bit 3 / SPI SCK / I2C SCL |
| Pin 14 | RC4/SDI/SDA — PORTC bit 4 / SPI SDI / I2C SDA |
| Pin 15 | RC5/SDO — PORTC bit 5 / SPI SDO |
| Pin 16 | RC6/TX/CK — PORTC bit 6 / USART TX / USART clock |
| Pin 17 | RC7/RX/DT — PORTC bit 7 / USART RX / USART data |
| Pin 18 | VSS — Ground reference |
| Pin 19 | VDD — Positive supply voltage |
| Pin 20 | RB0/INT — PORTB bit 0 / External interrupt |
| Pin 21 | RB1 — PORTB bit 1 |
| Pin 22 | RB2 — PORTB bit 2 |
| Pin 23 | RB3 — PORTB bit 3 |
| Pin 24 | RB4 — PORTB bit 4 |
| Pin 25 | RB5 — PORTB bit 5 |
| Pin 26 | RB6 — PORTB bit 6 |
| Pin 27 | RB7 — PORTB bit 7 |
| Pin 28 | RD0 — PORTD bit 0 |
| Pin 29 | RD1 — PORTD bit 1 |
| Pin 30 | RD2 — PORTD bit 2 |
| Pin 31 | RD3 — PORTD bit 3 |
| Pin 32 | RD4 — PORTD bit 4 |
| Pin 33 | RD5 — PORTD bit 5 |
| Pin 34 | RD6 — PORTD bit 6 |
| Pin 35 | RD7 — PORTD bit 7 |
| Pin 36 | RE0 — PORTE bit 0 |
| Pin 37 | RE1 — PORTE bit 1 |
| Pin 38 | RE2 — PORTE bit 2 |
| Pin 39 | VSS — Ground reference |
| Pin 40 | VDD — Positive supply voltage |
Typical Applications
PIC17LC42A-08/L is suitable for 7 applications: Industrial Automation Controllers, HVAC Control Boards, Motor Drive Sequencers, Legacy Embedded Systems, Security and Access Control Panels, Sensor Interface Modules, Automotive Aftermarket Controllers.
Industrial Automation Controllers
The PIC17LC42A-08/L fits industrial automation controllers because its 8 MHz RISC core executes instructions in 121 ns, fast enough to service multi-loop PID calculations in real time. The 33 general-purpose I/O pins handle limit switches, encoder inputs, relay drivers, and indicator LEDs without external muxing, while the four timers and two PWM modules drive brush DC motors or stepper sequences. Its EPROM-based 4 KB program memory allows in-circuit UV reprogramming during commissioning iterations. Watchdog timer and Power-on Reset guarantee recovery from supply brownouts on the factory floor. Compared with PIC16 mid-range devices, the PIC17 architecture delivers higher code density per instruction word and supports a 16-bit address bus that simplifies external memory expansion.
Recommended
HVAC Control Boards
HVAC control boards benefit from the PIC17LC42A-08/L because its 4 KB EPROM can hold heating/cooling curve lookup tables and weekly schedule logic, while the 232-byte RAM buffers thermostat setpoints and sensor history. The two PWM modules generate variable-speed fan drive signals, and the four timers schedule compressor anti-short-cycle delays. The 33 I/O pins support multiple temperature sensors, relay outputs for zone valves, and an alphanumeric LCD interface. Industrial temperature variants of this MCU operate reliably across the -40 C to +85 C range demanded by rooftop AHU enclosures. The USART links the board to a building management network using Modbus or BACnet gateways.
Recommended
Motor Drive Sequencers
Motor drive sequencers use the PIC17LC42A-08/L because its two PWM channels produce complementary drive waveforms for brushed DC or unipolar stepper motors, while the four timers deliver precise acceleration/deceleration ramps without software overhead. The 8 MHz instruction cycle (121 ns) supports trapezoidal and sinusoidal commutation profiles for low-RPM servo applications. The 33 I/O lines interface end-stop sensors, Hall-effect inputs, and enable/discrete gate-driver signals. The 4 KB EPROM accommodates complete motion-control firmware including S-curve profiles. The device's Harvard architecture prevents program-memory contention during high-speed PWM interrupts, a critical reliability feature for stepper systems.
Recommended
Legacy Embedded Systems
The PIC17LC42A-08/L is the natural fit for sustaining legacy embedded systems originally designed around the PIC17 architecture in the late 1990s. Its instruction set, register map, and interrupt structure match the original PIC17C42A silicon, allowing existing firmware to run unchanged while replacing damaged or EOL stock. The 40-pin DIP through-hole package preserves compatibility with vintage backplanes and wire-wrap prototypes. The EPROM window supports last-time repair cycles on fielded equipment. Engineers maintaining industrial controllers, scientific instruments, and aerospace ground support equipment find the PIC17LC42A a low-risk substitute for the obsolete PIC17C42A windowed samples.
Recommended
Security and Access Control Panels
Security and access control panels benefit from the PIC17LC42A-08/L because its 33 I/O pins scan a 4x4 keypad matrix, drive relay outputs for door strikes, and read magnetic contact sensors without external glue logic. The USART interfaces to a downstream master controller or radio modem for wireless reporting. The 4 KB EPROM stores zone definitions, user codes, and event log buffers, while 232-byte RAM handles debounce and timing states. The watchdog timer prevents lock-ups that could compromise intrusion detection. The 8 MHz instruction cycle supports multiple simultaneous tasks under a small RTOS-style scheduler. Industrial temperature variants operate in outdoor enclosures.
Recommended
Sensor Interface Modules
Sensor interface modules leverage the PIC17LC42A-08/L because its 4 KB EPROM stores linearization and calibration curves for thermocouples, RTDs, and load cells, while the four timers generate precision excitation waveforms for ratiometric bridges. The 8 MHz RISC core converts ADC samples (via external ADC) to engineering units at update rates above 100 Hz. The USART delivers digital readings to a host PLC or SCADA node using ASCII or Modbus protocols. The 33 I/O lines support multiplexed channel selection across 8-16 sensor inputs. The PIC17's Harvard architecture prevents ADC interrupt jitter from corrupting timing-critical PWM channels.
Recommended
Automotive Aftermarket Controllers
The PIC17LC42A-08/L fits automotive aftermarket controllers such as auxiliary lighting, alarm systems, and trailer brake modules because its 33 I/O drive relay banks and read switch inputs across 12 V vehicle buses. The four timers handle turn-signal cadence, PWM headlight dimming, and timeout counters, while the two PWM modules drive proportional solenoids. The 8 MHz instruction cycle processes input debouncing and event sequencing without missing interrupts. The 4 KB EPROM stores OEM-specific configuration tables that dealers can reprogram in the field. Note that for OEM automotive designs, Microchip recommends dsPIC33 AEC-Q100 qualified parts; the PIC17LC42A serves hobbyist and aftermarket segments only.
Recommended
Recommended Products Summary
Engineering reference data for PIC17LC42A-08/L — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC17C42A-08/L | PIC17LC42A-08I/L | PIC17LC42A-08/P | PIC17C42A-16E/P | PIC17C42A-25/PT | PIC17C42A-33I/P |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 40-DIP (0.600 inch) | 40-DIP (0.600 inch) - same | 40-DIP (0.600 inch) - same | 40-DIP (0.600 inch) - same | 40-DIP (0.600 inch) - same | 40-DIP (0.600 inch) - same | 40-DIP (0.600 inch) - same |
| Maximum Clock Frequency | 8 MHz | 8 MHz | 8 MHz | 8 MHz | 16 MHz | 25 MHz | 33 MHz |
| Program Memory Type | EPROM (UV-erasable) | OTPROM | EPROM | EPROM | OTPROM | OTPROM | OTPROM |
| Program Memory Size | 4 KB (2K x 16) | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB | 4 KB |
| RAM Size | 232 bytes | 232 bytes | 232 bytes | 232 bytes | 232 bytes | 232 bytes | 232 bytes |
| I/O Pin Count | 33 | 33 | 33 | 33 | 33 | 33 | 33 |
| Supply Voltage Family | Low-voltage CMOS (2.5 V to 6 V range) | Standard CMOS (4.5 V to 5.5 V) | Low-voltage CMOS, industrial temp | Low-voltage CMOS | Standard CMOS, extended temp | Standard CMOS | Standard CMOS, industrial temp |
| Lifecycle Status | Last-time-buy | Last-time-buy | Last-time-buy | Last-time-buy | Last-time-buy | Last-time-buy | Last-time-buy |
Key Differentiators
- EPROM windowed package supports field reprogramming via UV erasure (vs PIC17C42A-08/L)
- Low-voltage CMOS operation down to ~2.5 V (vs PIC17C42A-08/L)
- Through-hole 40-pin DIP form factor simplifies prototyping and rework (vs PIC17C42A-08/P)
Design Notes
The PIC17LC42A-08/L as a low-voltage CMOS variant operates across approximately 2.5 V to 6.0 V (verify against the manufacturer datasheet for the exact VDD range). Place a 100 nF ceramic decoupling capacitor within 5 mm of each VDD/VSS pin pair (pins 19/18 and 40/39), and add a single 10 uF bulk tantalum or ceramic capacitor near the device. The PIC17 architecture is sensitive to VDD ripple during ADC conversions (if external ADC is used); keep analog and digital VDD traces separate until they join at a single ferrite bead or pi filter. Decoupling must be solid because EPROM program writes during debug generate transient supply currents.
The PIC17LC42A-08/L uses EPROM (windowed ceramic) for program memory; parts with the ceramic window are sensitive to ambient light and must be socketed or covered with opaque tape during normal operation. Production builds should substitute the OTPROM-equivalent PIC17C42A-08/L, which lacks the window and is more reliable. Programmers must explicitly target the PIC17C4X device family; standard PIC16 programmers will fail. The maximum oscillator frequency of 8 MHz means RC oscillator configurations should be avoided for time-critical code paths - use a crystal or resonator instead. A common pitfall is forgetting to clear the watchdog timer in long interrupt service routines, which forces an unintended reset.
Route the OSC1/OSC2 traces (pins 8 and 9) as short, symmetric pairs and keep them away from high-current switching traces such as PWM-driven relay coils. The MCLR pin (pin 1) should have a 10 kohm pull-up to VDD and a 100 nF cap to ground to filter noise - omitting this is a frequent cause of spurious resets in industrial environments. Trace the USART TX/RX pair (pins 16/17) as a short differential pair if using RS-485 with an external transceiver. PORTA analog pins (2-7) should have separate analog ground returns if used with an external ADC; otherwise configure them as digital I/O to avoid noise coupling.
Compliance Information
RoHS/REACH compliance per Microchip packaging standards. Not AEC-Q100 qualified - the PIC17 family predates automotive-grade Microchip qualifications; use dsPIC33 AEC-Q100 parts for OEM automotive. Lead-free packaging confirmed; halogen-free status not explicitly published in the verified distributor data.
