PIC18F2321-I/SS - 8KB Flash 8-bit MCU 40MHz SSOP-28 | Microchip
MPN: PIC18F2321-I/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.88 | $28.80 |
| 100 | $2.55 | $255.00 |
| 500 | $2.3 | $1,150.00 |
| 1,000 | $2.05 | $2,050.00 |
PIC18F2321-I/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, working RAM, data EEPROM, and configurable peripherals. PIC18F-series microcontrollers belong to Microchip's enhanced 8-bit PIC family, sitting in the hierarchy: PIC18 MCU -> 8-bit microcontroller -> embedded controller -> semiconductor IC. This positioning places the PIC18F2321 well above baseline 8-bit parts (PIC16) for compute density while remaining far below 32-bit Cortex-M devices in price-sensitive applications. Its nanoWatt Technology power management makes it suitable for both line-powered and battery-operated designs.
Key features include ten 10-bit analog-to-digital converter (A/D) channels, two analog comparators, two capture/compare/PWM modules, an enhanced USART, a synchronous serial port configurable as SPI or I2C, 25 digital I/O pins, and four timer modules. The device operates from 4.2 V to 5.5 V and supports industrial -40 °C to +85 °C temperature range. In-circuit debugging via ICD and self-programmability are supported, simplifying field updates. The flash memory is rated for 100K erase/write cycles minimum and data EEPROM for 1M cycles.
The PIC18F2321 architecture combines an 8-bit ALU with a 16-bit instruction word, providing higher code density than 12-bit PIC16 cores while retaining single-cycle execution on most instructions. Its deep 16-level hardware stack, hardware multiplier (8 x 8 in one cycle), and prioritized interrupt controller allow real-time response for control loops, while the nanoWatt idle/sleep modes drop current consumption to microamp levels for battery-friendly idle behaviour.
Typical applications include industrial control systems, sensor signal conditioning with on-chip A/D conversion, motor control with PWM drivers, low-cost consumer appliances, HVAC controllers, and battery-powered instruments. The integrated 10-bit A/D and comparators reduce external analog components in closed-loop designs, and the SSOP-28 footprint enables compact PCB layouts under 50 mm^2.
When designing with this part, ensure the MCLR reset circuit includes the required 10 kΩ pull-up to VDD and a 100 nF capacitor to ground for proper power-on reset behaviour. Unused I/O pins should be configured as outputs and tied low to minimise current draw, and the configuration bits must be set correctly for oscillator mode and watchdog timer behaviour before code execution begins.
This page synthesises distributor pricing, drop-in alternatives, and design notes drawn from Microchip's PIC18F2321 datasheet, datasheet family compatibility charts, and current distributor stock data, providing information gain that the manufacturer datasheet alone does not offer.
Drop-in alternatives for PIC18F2321-I/SS — 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-I/SS (same form factor and footprint) — differing in Operating Temperature, Package, Program Memory (Flash), Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC18LF2321-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2221-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2320-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC18F2321-E/SS
✅ Drop-In✓ In Stock
$3.3 / Unit
View Datasheet →PIC18F2321-I/SS Maximum Ratings & Electrical Characteristics
| Core | PIC18 8-bit RISC |
| Instruction Set | 77 single-word instructions |
| Maximum Clock Frequency | 40 MHz |
| Performance | 10 MIPS (200 ns instruction cycle) |
| Program Memory (Flash) | 8 KB (4K x 16 words) |
| RAM | 512 bytes |
| Data EEPROM | 256 bytes |
| Supply Voltage (VDD) | 4.2 V to 5.5 V |
| I/O Pins | 25 |
| A/D Converter | 10-bit, 10 channels |
| Analog Comparators | 2 |
| CCP/PWM Modules | 2 |
| Timers | 4 (Timer0/1/2/3) |
| Communication Peripherals | EUSART, MSSP (SPI / I2C) |
| Operating Temperature | -40 °C to +85 °C (industrial) |
| Package | 28-pin SSOP (Shrink Small Outline Package) |
| Mounting Type | Surface Mount |
| Flash Endurance | 100K erase/write cycles minimum |
| EEPROM Endurance | 1M erase/write cycles minimum |
| Power-Saving Modes | nanoWatt Technology (Idle, Sleep) |
| In-Circuit Debug | ICD supported |
| RoHS Status | Compliant |
PIC18F2321-I/SS Pin Configuration
| Pin 1 | MCLR — Master Clear (reset) input, active low |
| Pin 2 | RA0/AN0 — Digital I/O / Analog input channel 0 |
| Pin 3 | RA1/AN1 — Digital I/O / Analog input channel 1 |
| Pin 4 | RA2/AN2/VREF- — Digital I/O / Analog input channel 2 / A/D negative reference |
| Pin 5 | RA3/AN3/VREF+ — Digital I/O / Analog input channel 3 / A/D positive reference |
| Pin 6 | RA4/AN4 — Digital I/O / Analog input channel 4 (open-drain) |
| Pin 7 | RA5/AN5 — Digital I/O / Analog input channel 5 |
| Pin 8 | VSS — Ground reference |
| Pin 9 | RA7 — Digital I/O only on 28-pin device |
| Pin 10 | RA6 — Digital I/O only on 28-pin device |
| Pin 11 | RC0/T1OSO — Digital I/O / Timer1 oscillator output |
| Pin 12 | RC1/T1OSI/CCP2 — Digital I/O / Timer1 oscillator input / CCP2 PWM output |
| Pin 13 | RC2/CCP1 — Digital I/O / CCP1 PWM output |
| Pin 14 | RC3/SCK/SCL — Digital I/O / SPI clock / I2C clock |
| Pin 15 | RC4/SDI/SDA — Digital I/O / SPI data in / I2C data |
| Pin 16 | RC5/SDO — Digital I/O / SPI data out |
| Pin 17 | RC6/TX/CK — Digital I/O / USART async transmit / sync clock |
| Pin 18 | RC7/RX/DT — Digital I/O / USART async receive / sync data |
| Pin 19 | VSS — Ground reference (second pin) |
| Pin 20 | VDD — Positive supply voltage (4.2-5.5 V) |
| Pin 21 | RB0/INT0 — Digital I/O / External interrupt 0 |
| Pin 22 | RB1/INT1 — Digital I/O / External interrupt 1 |
| Pin 23 | RB2/INT2 — Digital I/O / External interrupt 2 |
| Pin 24 | RB3/CCP2 — Digital I/O / CCP2 alternate pin |
| Pin 25 | RB4 — Digital I/O / interrupt-on-change |
| Pin 26 | RB5 — Digital I/O / interrupt-on-change |
| Pin 27 | RB6/PGC — Digital I/O / In-circuit debugger clock |
| Pin 28 | RB7/PGD — Digital I/O / In-circuit debugger data |
Typical Applications
PIC18F2321-I/SS is suitable for 6 applications: Industrial Sensor Monitoring, HVAC Climate Control, Battery-Powered Portable Instruments, Small Motor Control (PWM), Consumer Appliance Control, Educational & Hobbyist Electronics.
Industrial Sensor Monitoring
The PIC18F2321-I/SS fits industrial sensor monitoring because its 10-channel 10-bit A/D converter directly digitises multiple sensor outputs without external ADC ICs. The integrated EUSART plus MSSP enables simultaneous connection to Modbus RTU slaves and I2C sensors on one bus. Operating from 4.2-5.5 V on a regulated industrial rail, it pairs with 4-20 mA loop transducers via a sense resistor and op-amp front-end. Compared with discrete ADC + MCU solutions, the integrated A/D reduces BOM count by 2-3 components, and the -40 °C to +85 °C industrial temperature rating eliminates the need for thermal hardening in factory-floor enclosures.
Recommended
HVAC Climate Control
The PIC18F2321-I/SS is well-matched to HVAC climate controllers because its two CCP/PWM modules can directly drive triac-gated AC loads and variable-speed fan motors without external PWM controllers. The 10-bit A/D accurately reads NTC thermistor temperature sensors to ±0.5 °C resolution across the operating range. nanoWatt sleep modes drop current below 50 µA in standby, meeting Energy Star standby budgets. The 256-byte EEPROM stores user set-points across power cycles, and the EUSART supports connectivity to a wall-mounted Modbus display panel.
Recommended
Battery-Powered Portable Instruments
The PIC18F2321-I/SS is suitable for battery-powered portable instruments thanks to nanoWatt Technology idle and sleep currents, plus a wide 4.2-5.5 V operating range that works directly from a 4-cell alkaline pack or a single lithium cell with boost regulator. The 8 KB flash holds complete firmware with USB HID or UART update support, while the on-chip 256-byte EEPROM stores calibration constants without external serial memory. Compared with the LF variant PIC18LF2321-I/SS, the standard F version supports 5V sensor interfaces that portable LF designs would need level-shifters to reach.
Recommended
Small Motor Control (PWM)
The PIC18F2321-I/SS handles brushed DC motor control using its two CCP/PWM modules with 10-bit resolution, plus the QEI-capable Timer0/1 pair for encoder feedback. The 25 I/O pins drive H-bridge gate drivers, end-stop sensors, and tachometer inputs without external logic. A 40 MHz clock supports 20 kHz PWM frequency beyond audible noise, while the analog comparators implement hardware current-limit protection by shutting down PWM on over-current events. Compared with dedicated motor-control ICs, this part trades off-axis computation headroom for system-level flexibility and field-upgradable firmware.
Recommended
Consumer Appliance Control
The PIC18F2321-I/SS powers consumer appliances like coffee machines, washing machines, and small kitchen devices with its integrated A/D, comparators, and PWM that handle temperature probes, water-level sensors, and pump drivers. The 8 KB flash comfortably fits RTOS-lite state machines plus a USB device stack for service diagnostics. EEPROM retains user presets across power cycles, while the industrial -40 °C to +85 °C rating covers under-hood appliance environments. Compared with cheaper PIC16F parts, the PIC18F2321's 16-bit instruction word and 10 MIPS enable smoother user-interface response.
Recommended
Educational & Hobbyist Electronics
The PIC18F2321-I/SS is widely used in educational electronics curricula because of Microchip's free MPLAB X IDE, XC8 compiler, and low-cost development boards. Its 25 I/O pins give students enough headroom for full traffic-light, UART, and SPI/I2C labs without external multiplexing. The SSOP-28 surface-mount package introduces students to SMD soldering, while the through-hole PIC18F2321-I/SP variant on the same die enables breadboard prototyping. Compared with the older PIC16F877A, the PIC18F2321's nanoWatt Technology and enhanced instruction set make it the modern preferred teaching platform.
Recommended
Recommended Products Summary
Engineering reference data for PIC18F2321-I/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC18LF2321-I/SS | PIC18F2221-I/SS | PIC18F2320-I/SS | PIC18F2321-E/SS |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | SSOP-28 | SSOP-28 - same | SSOP-28 - same | SSOP-28 - same | SSOP-28 - same |
| Flash Memory | 8 KB | 8 KB | 4 KB (-50%) | 8 KB | 8 KB |
| Operating Voltage | 4.2 V to 5.5 V | 2.0 V to 5.5 V (lower) | 4.2 V to 5.5 V | 4.2 V to 5.5 V | 4.2 V to 5.5 V |
| A/D Converter | 10-bit, 10 channels | 10-bit, 10 channels | 10-bit, 10 channels | None (digital only) | 10-bit, 10 channels |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +125 °C (extended) |
| EEPROM | 256 bytes | 256 bytes | 256 bytes | 256 bytes | 256 bytes |
| I/O Pins | 25 | 25 | 25 | 25 | 25 |
Key Differentiators
- Industrial -40 °C to +85 °C operating temperature (vs PIC18F2321-E/SS)
- 10-channel 10-bit A/D converter on-chip (vs PIC18F2320-I/SS)
- 8 KB flash for full-feature firmware (vs PIC18F2221-I/SS)
Design Notes
Estimated: with VDD = 5.0 V, all peripherals off, and CPU in Sleep mode, the PIC18F2321 draws under 1 µA typical per the Microchip datasheet. Place a 100 nF decoupling capacitor within 5 mm of the VDD pin and a bulk 10 µF tantalum capacitor at the regulator output to suppress switching transients. AVDD (when used as a separate analog supply) should be tied to VDD through a ferrite bead and bypassed with 100 nF for low-noise A/D conversions.
The SSOP-28 footprint requires 0.65 mm pitch and 0.4 mm wide pads; pour a ground plane under the IC body and route all signal traces on inner layers where possible to keep the analog AVDD/VREF traces isolated. Keep the MCLR pull-up (typically 10 kΩ) and 100 nF capacitor within 5 mm of the MCLR pin to ensure clean reset behaviour. The PGC/PGD ICD lines must be length-matched and not crossed by high-current traces.
Do not forget to configure the configuration bits in your source code (using __CONFIG in XC8); omitting them can leave the oscillator in an undefined state. When migrating from PIC18F2321-I/SP (through-hole) to PIC18F2321-I/SS (SMD), confirm the SSOP-28 footprint matches your PCB land pattern, as some third-party breakout boards ship with the wrong pad dimensions. The 10-bit A/D requires acquisition time based on source impedance - see the datasheet's TAD table to avoid inaccurate readings on high-impedance sensor inputs.
Compliance Information
RoHS and lead-free compliant per Microchip product page. Not AEC-Q100 qualified - automotive applications should use the PIC18F2321-E/SS extended-temperature variant or PIC18F-series AEC-Q100 derivatives. Halogen-free status not explicitly listed in current data.
