PIC18F4321-E/P - 8-bit PIC MCU, 8KB Flash, 25MHz, 40-PDIP | Microchip
MPN: PIC18F4321-E/P ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.64 | $5.64 |
| 10 | $5.08 | $50.80 |
| 100 | $4.52 | $452.00 |
| 500 | $4.05 | $2,025.00 |
| 1,000 | $3.61 | $3,610.00 |
PIC18F4321-E/P Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU, memory, and programmable I/O peripherals, serving as the embedded "brain" in countless electronic products. Within Microchip's taxonomy, the PIC18F family sits in the high-performance tier of the 8-bit PIC family, above PIC10/12/16 baseline and mid-range parts and below the PIC24/dsPIC 16-bit family. The "F" in PIC18F denotes Flash program memory, supporting in-circuit serial programming (ICSP) and self-programming, while the "32" segment identifies the program-memory class within the family.
Key features include 13 channels of 10-bit Analog-to-Digital conversion, 2 analog comparators, 2 Capture/Compare/PWM (CCP) modules, an Enhanced CCP (ECCP) for motor control or full-bridge drive, an MSSP configurable as SPI or I2C, two USART modules, and nanoWatt Technology for ultra-low-power sleep modes. The 40-pin PDIP package provides generous I/O count with 36 digital I/O pins and exposes all major peripherals for breadboard-friendly prototyping.
Architecture-wise, the PIC18F4321 uses an 8-bit data path with a 16-bit instruction word, a hardware multiplier for 8x8 single-cycle multiplication, and a vectored interrupt controller with prioritized interrupts. The 10-bit ADC supports up to 13 channels with automatic acquisition and conversion, suitable for sensor reading at moderate rates. The nanoWatt Technology manager offers multiple idle and sleep modes that reduce quiescent current to the microampere range, supporting battery-powered designs.
Typical applications include industrial sensor interfaces, low-power remote data loggers, HVAC controller boards, appliance control panels, HVAC thermostats, motor-driver supervisory boards, and educational microcontroller platforms. The 25 MHz operation and 8KB Flash are well-matched to mid-complexity control loops, communication bridges, and sensor fusion tasks. Designers favor this part for its DIP package which simplifies hand-soldered prototypes and rework, and for the broad ecosystem of MPLAB X IDE, MCC code configurator, and XC8 compiler support.
Design consideration: although the -E/P variant is rated -40C to +125C, the lower "-I" grade (PIC18F4321-I/P, -40C to +85C) is more widely stocked; verify the temperature requirement before procurement. When designing with the ADC, ensure acquisition time meets source-impedance requirements or add an external buffer.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on standard manufacturer distributor listings.
Drop-in alternatives for PIC18F4321-E/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 PIC18F4321-E/P (same form factor and footprint) — differing in Package, Operating Temperature, Serial Interfaces, ADC, Program Memory (Flash).
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F4321-I/P
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4320-I/P
✅ Drop-In✓ In Stock
$4.05 / Unit
View Datasheet →PIC18F4221-I/P
✅ Drop-In✓ In Stock
$3.15 / Unit
View Datasheet →PIC18F4220-I/P
✅ Drop-In✓ In Stock
$4.78 / Unit
View Datasheet →PIC18F4320-E/P
✅ Drop-In✓ In Stock
$2.95 / Unit
View Datasheet →PIC18F4321-E/P Maximum Ratings & Electrical Characteristics
| Product Type | 8-bit Microcontroller (MCU) |
| Architecture | PIC18 enhanced Harvard, RISC |
| Program Memory (Flash) | 8 KB (4K x 16) |
| RAM | 512 bytes |
| EEPROM | 256 bytes |
| Instruction Set Size | 77 single-word instructions |
| Maximum CPU Speed | 25 MHz (10 MIPS) |
| Instruction Cycle | 100 ns at 40 MHz input / 25 MHz operation |
| ADC | 10-bit, up to 13 channels |
| Comparators | 2 analog comparators |
| CCP / ECCP Modules | 2 CCP + 1 ECCP |
| Serial Interfaces | 1 MSSP (SPI/I2C), 2 USART (EUSART) |
| I/O Pins | 36 digital I/O |
| Timers | 4 (Timer0/1/2/3) |
| nanoWatt Power Management | Yes (idle, sleep, deep sleep modes) |
| Self-Programming / ICSP | Yes |
| Operating Temperature Range | -40C to +125C (industrial "E" grade) |
| Package | 40-pin PDIP (0.600", 15.24 mm) |
| Mounting Type | Through-Hole |
| MSL Level | Not applicable (through-hole PDIP) |
PIC18F4321-E/P Pin Configuration
| Pin 1 | MCLR — Master Clear (reset) input, active low |
| Pin 2 | RA0/AN0 — PORTA bit 0 / analog channel 0 |
| Pin 3 | RA1/AN1 — PORTA bit 1 / analog channel 1 |
| Pin 4 | RA2/AN2/VREF- — PORTA bit 2 / analog channel 2 / ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — PORTA bit 3 / analog channel 3 / ADC VREF+ |
| Pin 6 | RA4/T0CKI — PORTA bit 4 / Timer0 clock input |
| Pin 7 | RA5/AN4/SS — PORTA bit 5 / analog channel 4 / SPI slave select |
| Pin 8 | RE0/RD/AN5 — PORTE bit 0 / read control / analog channel 5 |
| Pin 9 | RE1/WR/AN6 — PORTE bit 1 / write control / analog channel 6 |
| Pin 10 | RE2/CS/AN7 — PORTE bit 2 / chip select / analog channel 7 |
| Pin 11 | VDD — Positive supply voltage |
| Pin 12 | VSS — Ground reference |
| Pin 13 | OSC1/CLKI/RA7 — Oscillator input / external clock / PORTA bit 7 |
| Pin 14 | OSC2/CLKO/RA6 — Oscillator output / PORTA bit 6 |
| Pin 15 | RC0/T1OSO/T1CKI — PORTC bit 0 / Timer1 oscillator output / Timer1 clock |
| Pin 16 | RC1/T1OSI/CCP2 — PORTC bit 1 / Timer1 oscillator input / CCP2 |
| Pin 17 | RC2/CCP1 — PORTC bit 2 / CCP1 PWM output |
| Pin 18 | RC3/SCK/SCL — PORTC bit 3 / MSSP SPI clock / I2C clock |
| Pin 19 | RC4/SDI/SDA — PORTC bit 4 / MSSP SPI data in / I2C data |
| Pin 20 | RC5/SDO — PORTC bit 5 / MSSP SPI data out |
| Pin 21 | RC6/TX/CK — PORTC bit 6 / EUSART TX / EUSART clock |
| Pin 22 | RC7/RX/DT — PORTC bit 7 / EUSART RX / EUSART data |
| Pin 23 | RD0/PSP0 — PORTD bit 0 / parallel slave port bit 0 |
| Pin 24 | RD1/PSP1 — PORTD bit 1 / parallel slave port bit 1 |
| Pin 25 | RD2/PSP2 — PORTD bit 2 / parallel slave port bit 2 |
| Pin 26 | RD3/PSP3 — PORTD bit 3 / parallel slave port bit 3 |
| Pin 27 | RD4/PSP4 — PORTD bit 4 / parallel slave port bit 4 |
| Pin 28 | RD5/PSP5 — PORTD bit 5 / parallel slave port bit 5 |
| Pin 29 | RD6/PSP6 — PORTD bit 6 / parallel slave port bit 6 |
| Pin 30 | RD7/PSP7 — PORTD bit 7 / parallel slave port bit 7 |
| Pin 31 | VSS — Ground reference |
| Pin 32 | VDD — Positive supply voltage |
| Pin 33 | RB0/INT0/FLT0 — PORTB bit 0 / external interrupt 0 / ECCP fault input |
| Pin 34 | RB1/INT1 — PORTB bit 1 / external interrupt 1 |
| Pin 35 | RB2/INT2 — PORTB bit 2 / external interrupt 2 |
| Pin 36 | RB3/CCP2 — PORTB bit 3 / CCP2 alternate output |
| Pin 37 | RB4 — PORTB bit 4 (interrupt-on-change) |
| Pin 38 | RB5 — PORTB bit 5 (interrupt-on-change) |
| Pin 39 | RB6/PGC — PORTB bit 6 / ICSP clock (PGEC) |
| Pin 40 | RB7/PGD — PORTB bit 7 / ICSP data (PGED) |
Typical Applications
PIC18F4321-E/P is suitable for 7 applications: Industrial Sensor Interface Board, Low-Power Remote Data Logger, HVAC Controller Board, Appliance Control Panel, Motor Driver Supervisory Board, Educational Microcontroller Platform, Battery Management Monitor.
Industrial Sensor Interface Board
The PIC18F4321-E/P fits industrial sensor interface boards thanks to its 13-channel 10-bit ADC that reads multiple analog transducers simultaneously with selectable acquisition timing. Its 8 KB Flash holds sensor linearization tables and calibration constants, while 256 bytes of EEPROM stores non-volatile configuration data surviving power cycles. The 25 MHz core at 10 MIPS executes 100 ns per instruction, easily handling multi-sensor scanning, filtering, and Modbus RTU transmission over the EUSART. The -40C to +125C extended industrial temperature grade ensures reliable operation in factory-floor cabinets and outdoor enclosures. Place it between a sensor connector header and an RS-485 transceiver, using the MSSP for SPI-based ADC stacking or as an I2C gateway.
Recommended
Low-Power Remote Data Logger
The PIC18F4321-E/P suits battery-powered remote data loggers through its nanoWatt Technology power manager that drops quiescent current to microampere levels during sleep. With 8 KB Flash for compressed logging algorithms and 256 bytes of EEPROM for sample-timestamp metadata, the device can wake on timer interrupt, sample an analog sensor through the 10-bit ADC, store the result in Flash, and return to sleep for months on a single battery. The EUSART/MSSP can also wake on UART/SPI activity for command-mode diagnostics. At 25 MHz operation, peak active current is modest and easily offset by long sleep intervals, supporting years of unattended operation in remote installations.
Recommended
HVAC Controller Board
The PIC18F4321-E/P drives HVAC control panels using its 2 CCP plus 1 ECCP module for PWM-controlled damper motors, triac-fired heating elements, and variable-speed fan drives. The 13-channel 10-bit ADC reads thermistor temperature sensors, pressure transducers, and airflow meters, while the EUSART interfaces to a wall thermostat display or a Modbus building-automation network. The -40C to +125C extended temperature rating tolerates attic and rooftop cabinet environments, and 8 KB Flash stores seasonal scheduling tables plus learned-control algorithms. A real-time calendar can be implemented in software using Timer1 with an external 32.768 kHz crystal for time-of-day scheduling.
Recommended
Appliance Control Panel
The PIC18F4321-E/P anchors washing-machine, dishwasher, and oven control panels where its 36 digital I/O pins drive 7-segment or LCD displays, button matrices, rotary encoders, and buzzer feedback. The 25 MHz core runs the main state machine that sequences wash cycles, monitors water-level sensors through the ADC, and controls motor direction via the ECCP full-bridge PWM module. Self-programming Flash allows field firmware updates via ICSP, useful for post-launch bug fixes and feature additions. The -40C to +125C temperature grade survives oven-control proximity heat, and nanoWatt Technology puts the panel in deep sleep when the appliance is idle, meeting ENERGY STAR standby budgets.
Recommended
Motor Driver Supervisory Board
The PIC18F4321-E/P supervises brushless DC and stepper motor drivers using its ECCP module to generate complementary PWM with programmable dead-band, hardware fault inputs that trip on overcurrent, and the 10-bit ADC to sense motor current via a hall-effect or shunt amplifier. The MSSP can configure as SPI to read encoder feedback at high speed, while the EUSART links to a host controller or HMI display. At 10 MIPS, the device executes FOC commutation tables and ramps with deterministic timing, well within its 100 ns instruction cycle. Extended -40C to +125C operation is essential for motor compartments where ambient temperatures peak during high-torque stalls.
Recommended
Educational Microcontroller Platform
The PIC18F4321-E/P is an excellent teaching platform because its 40-pin PDIP form factor fits standard breadboards and IC sockets, allowing students to prototype without soldering. The 8 KB Flash and 512 bytes RAM are sized to teach embedded C programming without overwhelming beginners, while the rich peripheral set (10-bit ADC, MSSP SPI/I2C, USART, CCP/PWM, comparators) introduces all the building blocks used in industrial designs. MPLAB X with the XC8 C compiler and PICkit 4 programmer are free for education, supported by Microchip's academic program. The -40C to +125C rating lets the same hardware serve labs, capstone projects, and outdoor field exercises without temperature derating.
Recommended
Battery Management Monitor
The PIC18F4321-E/P monitors multi-cell battery packs via its 13-channel 10-bit ADC, reading individual cell voltages, pack current via a shunt amplifier, and NTC thermistor temperatures for thermal protection. The ECCP module can PWM-control a balancing FET array, while the MSSP reads a battery-identification EEPROM or gas-gauge IC over I2C. The 256 bytes of EEPROM store learned-capacity calibration data that persists across charge cycles. The -40C to +125C extended temperature grade handles under-hood automotive environments and outdoor solar-storage cabinets. nanoWatt Technology puts the monitor in microampere sleep between samples, preserving battery life over multi-year deployments.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F4321-E/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F4321-I/P | PIC18F4320-I/P | PIC18F4320-E/P | PIC18F4221-I/P | PIC18F4220-I/P |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 40-pin PDIP | 40-pin PDIP - same | 40-pin PDIP - same | 40-pin PDIP - same | 40-pin PDIP - same | 40-pin PDIP - same |
| Program Memory (Flash) | 8 KB | 8 KB | 16 KB | 16 KB | 4 KB | 4 KB |
| RAM | 512 bytes | 512 bytes | 768 bytes | 768 bytes | 256 bytes | 256 bytes |
| EEPROM | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes |
| Maximum CPU Speed | 25 MHz (10 MIPS) | 25 MHz (10 MIPS) | 25 MHz (10 MIPS) | 25 MHz (10 MIPS) | 25 MHz (10 MIPS) | 25 MHz (10 MIPS) |
| ADC Channels | 13 x 10-bit | 13 x 10-bit | 11 x 10-bit | 11 x 10-bit | 9 x 10-bit | 9 x 10-bit |
| Operating Temperature | -40C to +125C (E grade) | -40C to +85C (I grade) | -40C to +85C (I grade) | -40C to +125C (E grade) | -40C to +85C (I grade) | -40C to +85C (I grade) |
Key Differentiators
- Extended industrial temperature grade -40C to +125C in 40-pin PDIP (vs PIC18F4321-I/P)
- 13-channel 10-bit ADC vs lower-channel siblings (vs PIC18F4320-I/P)
- ECCP module for full-bridge PWM motor control (vs PIC18F4221-I/P)
Design Notes
Use decoupling capacitors on every VDD/VSS pair of the PIC18F4321-E/P: a 100 nF ceramic as close as possible to pins 11-12 and another 100 nF at pins 31-32, plus a bulk 10 uF tantalum or aluminum near the MCU. The 40-pin PDIP has two VDD/VSS pin pairs (11/12 and 31/32) per the Microchip PIC18F4321 family datasheet (DS39689B), and bypassing both pairs is critical because the internal ADC and analog references draw transient current that can couple into the digital supply without local decoupling. Add a ferrite bead or small inductor in series with VDD for designs with switching converters nearby.
Place the 25 MHz crystal or resonator (or external clock source) within 1 cm of the OSC1/OSC2 pins (13/14) and guard it with a ground pour to minimize EMI. Keep ADC analog traces (RA0-RA5, RE0-RE2) away from switching nodes like PWM outputs (RC2/CCP1, RB3/CCP2) and route them with ground-plane shielding. The MCLR pin (1) requires a 10 kohm pull-up to VDD and a 100 nF cap to ground for clean reset behavior; do not leave MCLR floating. For ICSP programming, dedicate pins 39/40 (RB6/RB7) and add a 6-pin header on the PCB for field firmware updates.
Estimated: the PIC18F4321-E/P is rated 4.2-5.5V on VDD (typical PIC18F family range, exact value not in verified data). Do NOT use the LF variant (PIC18LF4321-I/P, 2.0-3.6V) as a 5V drop-in - I/O pin VIH/VIH and analog VREF behavior differ. When using the ADC, ensure the analog input source impedance is less than 2.5 kohm to avoid acquisition-time errors, or buffer the signal with an op-amp. The CCP/ECCP modules share timers with the MSSP SPI clock generator in some configurations; consult the datasheet peripheral-mapping tables to avoid conflicts when both SPI and PWM are active simultaneously.
The PIC18F4321-E/P in PDIP package is rated for -40C to +125C junction temperature but operates at low current (typically <50 mA active, <10 uA sleep) so thermal management is rarely a concern. However, in fully-loaded designs where all 36 I/O pins drive 20 mA loads simultaneously, total I/O current can reach 200 mA, raising die temperature noticeably. Estimate: at 5V VDD with 200 mA load, package dissipation is about 1W and the PDIP theta_JA of ~70 C/W yields a 70 C rise above ambient - well within the 125 C limit but warrants PCB thermal relief (copper pour) in high-temperature environments like under-hood automotive.
Compliance Information
RoHS, REACH, lead-free, and halogen-free status not explicitly stated in verified distributor snippets. Microchip parts are typically RoHS compliant but this should be confirmed via the manufacturer product page or a formal compliance certificate (CofC) before production use. AEC-Q100 qualification not applicable for general-purpose industrial microcontrollers - select PIC18F "-Q" automotive variants for AEC-Q100.
