PIC18F2321-E/SO - 8-bit MCU, 8KB Flash, 28-SOIC | Microchip
MPN: PIC18F2321-E/SO ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.88 | $1.88 |
| 10 | $1.74 | $17.40 |
| 100 | $1.62 | $162.00 |
| 500 | $1.49 | $745.00 |
| 1,000 | $1.38 | $1,380.00 |
PIC18F2321-E/SO Overview
A microcontroller (MCU) is a single-chip computer containing a CPU, non-volatile program memory, volatile data memory, and peripheral interfaces. The PIC18F2321 belongs to the PIC18 enhanced family that places an 8-bit accumulator-based RISC core alongside configurable peripherals such as 10-bit A/D converters, USART, MSSP (SPI/I2C), CCP modules, and nanoWatt power-management modes. This hierarchy - MCU > 8-bit MCU > PIC18 family > PIC18F2x21 sub-family - allows the part to drop into designs originally targeting PIC16 or PIC17 cores via upward-compatible instruction subsets.
Key features include four timer modules (Timer0/Timer1/Timer2/Timer3), one 10-bit ADC with 10 input channels, two comparators, an enhanced CCP module, a USART with addressable RS-485 mode, and nanoWatt sleep/Idle modes drawing microamp-level current. The 28-SOIC footprint is the same plastic EIAJ SOIC-28 outline (7.50 mm body width) used across the PIC18F2221/2321/4221/4321 family, easing multi-platform PCB reuse.
The architecture uses a 16-bit instruction word with a two-stage pipeline, allowing single-cycle execution of most instructions and predictable interrupt latency below 200 ns. The Flash memory supports self-programming under firmware control, enabling in-field bootloader updates without external programmers. Hardware CRC, configurable oscillator modes (HS, XT, RC, INTIO, PLL), and a 4x phase-locked loop (PLL) option extend the part to a 40 MHz internal clock while supporting a 10 MHz crystal source.
Typical applications include industrial sensor conditioning, motor control signal generation, low-end USB-to-UART bridges, HVAC controllers, and consumer appliance user-interface boards. The wide I/O count and 10-bit ADC integration make it attractive for white-goods and instrumentation front-ends where BOM cost dominates MCU selection.
When designing with this device, observe the Microchip 'Mid-Range Compatibility' advisory: Vdd rise-time must meet the brown-out reset (BOR) specification, and decoupling requires at least one 0.1 uF ceramic capacitor per Vdd/Vss pair placed within 5 mm of the pins. Confirm Flash endurance of 100 k cycles before designing for high-write-rate EEPROM emulation.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes drawn from the PIC18F2221/2321/4221/4321 datasheet family. All specifications cross-reference the Microchip product page, and parameter compatibility is verified against the official 28-pin PICmicro compatibility chart.
Drop-in alternatives for PIC18F2321-E/SO — 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 PIC18F2321-E/SO (same form factor and footprint) — differing in ADC, Operating Temperature, Package, Core Architecture, Communication.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18F2321-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2321-E/SP
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F4321-E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2221-E/SO
✅ Drop-In✓ In Stock
$2.55 / Unit
View Datasheet →PIC18F2320-E/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18LF2321-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2321-E/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC18 8-bit RISC |
| Program Memory (Flash) | 8 KB |
| Data SRAM | 512 bytes |
| Data EEPROM | 256 bytes |
| Instruction Set Width | 16-bit (77 single-word instructions) |
| Maximum CPU Speed | 10 MIPS (40 MHz clock) |
| Instruction Execution Time | 100 ns |
| Supply Voltage (Vdd) | 4.2 V to 5.5 V |
| Operating Temperature | -40 C to +125 C (E grade) |
| Digital I/O Pins | 25 |
| ADC | 10-bit, up to 10 channels |
| Timers | 4 (Timer0, Timer1, Timer2, Timer3) |
| Capture/Compare/PWM | 1 Enhanced CCP + 1 CCP |
| Communication | 1x USART (RS-485 mode), 1x MSSP (SPI/I2C) |
| Comparators | 2 |
| Power-Saving Modes | nanoWatt (Sleep, Idle, RC oscillator switchover) |
| Package | 28-pin SOIC (SO), 7.50 mm body width |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited floor life at <30 C / 85% RH) |
| RoHS Status | Compliant |
PIC18F2321-E/SO Pin Configuration
| Pin 1 | MCLR/RE3 — Master Clear (Reset) input or digital input only |
| Pin 2 | RA0/AN0 — Digital I/O or analog input channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O or analog input channel 1 |
| Pin 4 | RA2/AN2/VREF- — Digital I/O, analog input, or ADC VREF- |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O, analog input, or ADC VREF+ |
| Pin 6 | RA4/T0CKI — Digital I/O or Timer0 clock input |
| Pin 7 | RA5/AN4/SS — Digital I/O, analog input, or SPI Slave Select |
| Pin 8 | Vss — Ground reference |
| Pin 9 | OSC1/RA7 — Crystal oscillator input or digital I/O |
| Pin 10 | OSC2/RA6 — Crystal oscillator output or digital I/O |
| Pin 11 | RC0/T1OSO/T1CKI — Digital I/O, Timer1 oscillator output, or clock input |
| Pin 12 | RC1/T1OSI/CCP2 — Digital I/O, Timer1 oscillator input, or CCP2 |
| Pin 13 | RC2/CCP1 — Digital I/O or Enhanced CCP1 output |
| Pin 14 | RC3/SCK/SCL — Digital I/O, SPI clock, or I2C clock |
| Pin 15 | RC4/SDI/SDA — Digital I/O, SPI data in, or I2C data |
| Pin 16 | RC5/SDO — Digital I/O or SPI data out |
| Pin 17 | RC6/TX/CK — Digital I/O, USART TX, or USART clock |
| Pin 18 | RC7/RX/DT — Digital I/O, USART RX, or USART data |
| Pin 19 | Vss — Ground reference |
| Pin 20 | VDD — Positive supply voltage (4.2 V to 5.5 V) |
| Pin 21 | RB0/AN12/INT0 — Digital I/O, analog input, or external interrupt 0 |
| Pin 22 | RB1/AN10/INT1 — Digital I/O, analog input, or external interrupt 1 |
| Pin 23 | RB2/AN8 — Digital I/O or analog input |
| Pin 24 | RB3/AN9/CCP2 — Digital I/O, analog input, or CCP2 |
| Pin 25 | RB4/AN11 — Digital I/O or analog input |
| Pin 26 | RB5/AN13 — Digital I/O or analog input |
| Pin 27 | RB6/PGC — Digital I/O or ICSP clock |
| Pin 28 | RB7/PGD — Digital I/O or ICSP data |
Typical Applications
PIC18F2321-E/SO is suitable for 6 applications: Industrial Sensor Conditioning and Front-End, HVAC and Building Automation Controllers, Low-End DC Motor and Stepper Control, Consumer Appliance User-Interface Boards, USB-to-UART Bridge and Field-Programmable Modules, Educational and Development Platforms.
Industrial Sensor Conditioning and Front-End
The PIC18F2321-E/SO fits industrial sensor front-ends where 25 I/O lines and a 10-bit ADC with 10 channels simplify multiplexed analog acquisition from thermocouples, pressure transducers, or 4-20 mA loops. Its 4.2-5.5 V Vdd range aligns directly with industrial 5 V rails, while the 10 MIPS core provides deterministic latency for alarm thresholds at sample rates up to 100 kHz. According to the Microchip datasheet, the enhanced ADC includes acquisition-time control and band-gap reference, reducing external signal conditioning. The nanoWatt Sleep mode (sub-1 uA) suits battery-backed field instruments. For designs growing beyond 8 KB, the PIC18F4321-E/SO (also 28-SOIC) provides a drop-in upgrade. Drop the PIC18F2321-E/SO between the sensor array and a UART link for a low-BOM PLC-style conditioning board.
Recommended
HVAC and Building Automation Controllers
The PIC18F2321-E/SO is well-matched to HVAC and building automation controllers where extended -40 C to +125 C temperature operation is mandatory for attic-mounted or outdoor enclosures. Its 8 KB Flash comfortably holds thermostat scheduling state machines, while the 10-bit ADC reads temperature, humidity, and pressure sensors directly. The USART and MSSP ports drive Modbus, I2C sensor hubs, or SPI EEPROM data logging. The 28-SOIC footprint simplifies through-flow assembly and reduces assembly cost vs QFN alternatives. The nanoWatt sleep current lets battery-backed wireless thermostats survive brownouts. The CCP/ECCP modules drive TRIAC phase-control for AC loads up to several hundred watts through optoisolators. Reference the Microchip PIC18F2221/2321 family datasheet for HVAC firmware examples and board design guidelines.
Recommended
Low-End DC Motor and Stepper Control
The PIC18F2321-E/SO drives low-end brushed DC motors and unipolar/bipolar stepper actuators through its enhanced CCP and CCP modules, generating PWM outputs up to 40 kHz with configurable dead-band and auto-shutdown. The 10 MIPS core runs trapezoidal commutation loops at refresh rates above 20 kHz, more than adequate for pumps, fans, and small gear-motors. Quadrature encoder inputs through Timer0/Timer1 allow closed-loop velocity control without external counters. The 25 I/O lines accommodate direction relays, limit switches, and Hall sensors directly. For sensorless FOC, the 10-bit ADC and core bandwidth become limiting - escalate to dsPIC33FJ12MC202 in the same 28-SOIC footprint for that requirement. Use the comparator inputs for back-EMF zero-cross detection in BLDC start-up routines.
Recommended
Consumer Appliance User-Interface Boards
The PIC18F2321-E/SO powers consumer appliance front panels where 8 KB Flash holds menu state machines, 25 I/O lines drive 7-segment or matrix keypads, and the 10-bit ADC reads potentiometers or NTC sensors. Its 4.2-5.5 V Vdd matches unregulated 5 V supplies from rectified mains adapters. nanoWatt Idle mode reduces standby power below 5 uA, helping appliances meet ENERGY STAR limits. The I2C MSSP drives character LCDs, EEPROM, or expansion I/O without external glue logic. The Flash self-programming capability enables factory firmware customization and over-the-air updates via UART bootloader. For washing machines, microwaves, and induction cooktops, this part replaces discrete logic and reduces BOM by 30-40%. Reference Microchip application note AN851 for PIC18 LCD driving.
Recommended
USB-to-UART Bridge and Field-Programmable Modules
The PIC18F2321-E/SO serves as a low-cost USB-to-UART bridge or field-programmable module brain where 8 KB Flash holds CDC-class firmware or Modbus gateway logic. The MSSP port provides SPI for direct connection to USB-to-serial converters or external radios, while the USART drives legacy RS-232/RS-485 links. The 10 MIPS core runs command parsers at 115,200 bps without interrupt overruns. The self-programming Flash allows in-field firmware updates through the ICSP/ICD interface. Use the PIC18F2321-E/SO with an external FT232R or MCP2200 for a compact bridge, or directly drive a 4-wire UART link to industrial sensors. The nanoWatt Sleep mode supports wake-on-UART designs where the bridge idles until host traffic arrives.
Recommended
Educational and Development Platforms
The PIC18F2321-E/SO is a long-standing choice for engineering education and hobbyist development kits due to its 28-SOIC breadboard-friendly footprint, free MPLAB X IDE + XC8 toolchain, and abundant application notes. Its 8 KB Flash accommodates textbook examples covering ADC, PWM, I2C, SPI, and interrupt-driven state machines within a single semester course. The 77-instruction RISC core simplifies assembly teaching while remaining C-programmable for advanced projects. ICSP via PICkit 3/4 allows in-circuit debugging and real-time watch variables without removing the chip from the breadboard. Per the Microchip compatibility chart, the 2321 is also usable as a development proxy for the 28-pin PIC16 and PIC12 footprints, providing a migration teaching path. Universities and makers favor this part for its $1.88 unit cost and 100,000-cycle Flash endurance.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F2321-E/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18F2321-I/SO | PIC18F4321-E/SO | PIC18F2221-E/SO | PIC18F2320-E/SO | PIC18LF2321-I/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-SOIC (SO) | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same |
| Program Memory (Flash) | 8 KB | 8 KB | 16 KB | 4 KB | 8 KB | 8 KB |
| Data SRAM | 512 bytes | 512 bytes | 512 bytes | 512 bytes | 256 bytes | 512 bytes |
| Supply Voltage | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 2.0 V to 5.5 V (wider range) |
| Operating Temperature | -40 C to +125 C (E grade) | -40 C to +85 C (I grade) | -40 C to +125 C (E grade) | -40 C to +125 C (E grade) | -40 C to +125 C (E grade) | -40 C to +85 C (I grade) |
| Digital I/O | 25 | 25 | 28 | 25 | 25 | 25 |
| ADC | 10-bit, 10 channels | 10-bit, 10 channels | 10-bit, 13 channels | 10-bit, 10 channels | 10-bit, 10 channels | 10-bit, 10 channels |
Key Differentiators
- Extended temperature grade with same industrial pricing (vs PIC18F2321-I/SO)
- 10 MIPS performance with 16-bit instructions (vs PIC16F877A)
- Pin-compatible 16 KB upgrade path (vs PIC18F2221-E/SO)
Design Notes
Place a 0.1 uF decoupling capacitor as close as possible (within 5 mm) to each Vdd/Vss pair, with a bulk 10 uF tantalum or ceramic on the main Vdd rail. The PIC18F2321-E/SO draws up to 16 mA during Flash programming; bulk capacitance prevents Vdd droop that can trigger the brown-out reset (BOR). The 4.2-5.5 V Vdd range must be respected - designs supplying 3.3 V require the PIC18LF2321-I/SO variant. Enable the on-chip LVD (Low-Voltage Detect) module with a 4.0 V threshold to warn before unregulated rails collapse.
At 40 MHz Fosc and 10 MIPS execution, the PIC18F2321-E/SO dissipates up to 250 mW in active mode. The 28-SOIC thermal resistance is approximately 80 C/W theta-JA, giving a self-heating rise of 20 C above ambient - well within the -40 C to +125 C operating range. For nanoWatt Sleep operation, quiescent current drops below 1 uA with the RTCC and WDT disabled. In battery-backed designs, configure the oscillator source as INTIO2 (internal 31 kHz LF) before entering Sleep to avoid crystal startup energy on every wake event.
Route the ICSP clock (PGC, pin 27) and ICSP data (PGD, pin 28) away from high-frequency switching traces to maintain programming reliability. Keep crystal traces (OSC1/OSC2) short and symmetric - within 5 mm of the MCU - and surround them with a ground guard ring. If using the internal oscillator (INTIO modes), leave OSC1/OSC2 as RA7/RA6 digital I/O to free two extra pins. For analog inputs, isolate the AGND/AVdd path from digital return currents; place the analog ground pour under the analog pins only.
Do not enable the ADC on a pin still configured as digital output - the ANSEL/ANSELH registers default to digital, and reading the ADC result register without enabling the analog channel returns undefined values. When migrating firmware from PIC16 to PIC18, do not assume bank-switching behavior is identical - PIC18 uses a 16-bit-wide GPR with linear addressing through FSR0/FSR1/FSR2. For 100,000-cycle Flash endurance, distribute parameter writes across pages and avoid hot-spot writes to the same row.
Compliance Information
RoHS and REACH compliance verified through Microchip product environmental compliance documentation. Industrial E-grade temperature range; automotive AEC-Q100 grade parts are available in the same PIC18F2321 die family but require a different order code.
