PIC16C55A-20I/SP - 8-bit OTP MCU, 20MHz, 768B, SPDIP-28 | Microchip
MPN: PIC16C55A-20I/SP β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.86 | $4.86 |
| 10 | $4.37 | $43.70 |
| 100 | $3.83 | $383.00 |
| 500 | $3.42 | $1,710.00 |
| 1,000 | $3.01 | $3,010.00 |
PIC16C55A-20I/SP Overview
A microcontroller (MCU) is a single-chip computer containing a CPU, program memory, working RAM, and peripherals such as I/O ports, timers, and interrupt logic. Within the broader taxonomy, the PIC16C55A belongs to the 8-bit MCU class -> RISC MCU -> Harvard-architecture MCU -> embedded controller -> semiconductor. The PIC16C5X family uses a 12-bit instruction word with a 2:1 code compression advantage over competing 8-bit MCUs of its era, and its symmetric instruction set reduces development time significantly.
Key features of the PIC16C55A-20I/SP include seven or eight special function hardware registers, a two-level deep hardware stack, and direct, indirect, and relative addressing modes for both data and instructions. An 8-bit real-time clock/counter (TMR0) with a programmable prescaler is integrated, along with a watchdog timer for unattended operation. The architecture uses a modified Harvard design with separate program and data buses for deterministic instruction execution.
Typical applications include appliance control, automotive subsystems, industrial process control, security and access systems, and low-end consumer products where cost-sensitive embedded control is needed. The device is supported by the PICmicro Mid-Range Reference Manual and the MPLAB PM3 Universal Device Programmer for code development and OTP programming.
When designing with this part, note that OTP memory cannot be reprogrammed in-circuit - firmware bugs require part replacement. Provide a clean +5V supply with adequate decoupling (100 nF plus 10 uF bulk) on VDD, and respect the 5V absolute maximum rating when driving industrial loads. The PIC16C55A is rated for 5V operation only and does not support the wider voltage range of later Flash-based PIC16F parts.
This page synthesizes distributor pricing, drop-in pin-compatible alternatives within the PIC16C5X family, lifecycle status, and practical design notes not consolidated in any single manufacturer document.
Drop-in alternatives for PIC16C55A-20I/SP β 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 PIC16C55A-20I/SP (same form factor and footprint) β differing in Mounting Type, Program Memory Size, RoHS Status, Operating Temperature, Package.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C55A-20I/P
β Drop-Inβ In Stock
$1.6 / Unit
View Datasheet βPIC16C55A-20/SP
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55A-04I/P
β Drop-Inπ Reference alternative (not in catalog)
PIC16C56A-20I/SP
β Drop-Inπ Reference alternative (not in catalog)
PIC16C54A-20I/P
β Drop-Inβ In Stock
$1.38 / Unit
View Datasheet βPIC16C55A-20I/SP Maximum Ratings & Electrical Characteristics
| Core | PIC16C 8-bit RISC |
| Program Memory Type | OTP (One-Time Programmable) |
| Program Memory Size | 768 bytes (512 x 12) |
| RAM Size | 24 bytes |
| Maximum Clock Frequency | 20 MHz |
| Operating Voltage (VDD) | 4.5 V to 5.5 V |
| I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0 with prescaler) |
| Watchdog Timer | Yes |
| Hardware Stack | 2-level |
| Instruction Word Width | 12-bit |
| Operating Temperature | -40C to +85C (Industrial) |
| Package | SPDIP-28 |
| Mounting Type | Through-Hole |
| RoHS Status | Compliant |
PIC16C55A-20I/SP Pin Configuration
| Pin 1 | VDD β Positive supply voltage (+5V) |
| Pin 2 | OSC1/CLKIN β Oscillator input / external clock |
| Pin 3 | OSC2/CLKOUT β Oscillator output |
| Pin 4 | MCLR β Master Clear (reset, active low) |
| Pin 5 | VSS β Ground reference |
| Pin 6 | RA0 β Port A bit 0 (bidirectional I/O) |
| Pin 7 | RA1 β Port A bit 1 (bidirectional I/O) |
| Pin 8 | RA2 β Port A bit 2 (bidirectional I/O) |
| Pin 9 | RA3 β Port A bit 3 (bidirectional I/O) |
| Pin 10 | T0CKI β Timer0 clock input (shared with RA4) |
| Pin 11 | RA4 β Port A bit 4 / T0CKI |
| Pin 12 | RB0/INT β Port B bit 0 / external interrupt |
| Pin 13 | RB1 β Port B bit 1 (bidirectional I/O) |
| Pin 14 | RB2 β Port B bit 2 (bidirectional I/O) |
| Pin 15 | RB3 β Port B bit 3 (bidirectional I/O) |
| Pin 16 | RB4 β Port B bit 4 (bidirectional I/O) |
| Pin 17 | RB5 β Port B bit 5 (bidirectional I/O) |
| Pin 18 | RB6 β Port B bit 6 (bidirectional I/O) |
| Pin 19 | RB7 β Port B bit 7 (bidirectional I/O) |
| Pin 20 | VSS β Ground reference |
| Pin 21 | RC0 β Port C bit 0 (bidirectional I/O) |
| Pin 22 | RC1 β Port C bit 1 (bidirectional I/O) |
| Pin 23 | RC2 β Port C bit 2 (bidirectional I/O) |
| Pin 24 | RC3 β Port C bit 3 (bidirectional I/O) |
| Pin 25 | RC4 β Port C bit 4 (bidirectional I/O) |
| Pin 26 | RC5 β Port C bit 5 (bidirectional I/O) |
| Pin 27 | RC6 β Port C bit 6 (bidirectional I/O) |
| Pin 28 | RC7 β Port C bit 7 (bidirectional I/O) |
Typical Applications
PIC16C55A-20I/SP is suitable for 6 applications: Home Appliance Control, Industrial Sensor Interface, Automotive Body Electronics (Non-Safety), Security and Access Control Panels, Battery-Powered Toys and Consumer Gadgets, Hobby and Education Development Boards.
Home Appliance Control
The PIC16C55A-20I/SP is well-suited to home appliance controllers (washing machines, microwave ovens, dishwashers) where cost is critical and firmware is stable in production. Its 768 bytes of OTP memory holds multi-segment timing routines for motor control, sensor polling, and relay sequencing, while the 8-bit TMR0 with watchdog timer handles debounced keypad scans and failsafe resets. The 20 I/O pins drive 7-segment displays, status LEDs, and triac optocouplers directly, and the industrial -40C to +85C temperature range covers unheated garage and basement installations. Single 5V supply operation simplifies the AC-DC converter design.
Recommended
Industrial Sensor Interface
For low-speed industrial sensors (thermistors, level switches, photoelectric sensors) the PIC16C55A-20I/SP delivers deterministic 8-bit RISC execution and a single 5V supply that simplifies integration with analog front-ends. The 24 bytes of RAM support a small cyclic buffer for averaging ADC-free ratiometric measurements read through digital I/O, and the hardware watchdog prevents lockup in unattended installations. Twenty I/O pins multiplex many discrete sensors without external logic, and the SPDIP-28 package simplifies hand-soldered prototypes. Designers should add TVS diodes on every I/O exposed to the field.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16C55A-20I/SP powers non-safety body modules (window lift timers, mirror controllers, simple interior lighting) where cost dominates over AEC-Q100 qualification. The industrial -40C to +85C range covers cabin environments, and the robust CMOS process tolerates automotive electrical transients when paired with external TVS protection. The 20 MHz clock gives sub-microsecond bit-banging response for LIN-style single-wire comms, and the OTP memory secures production firmware against unauthorized field reprogramming. Designers must still validate EMC per OEM standards.
Recommended
Security and Access Control Panels
Security keypads, RFID readers, and small alarm panels leverage the PIC16C55A-20I/SP's 20 I/O pins for 4x4 matrix keypads, status LEDs, buzzer drivers, and relay outputs without external glue logic. The 768-byte OTP memory stores PIN-verification routines and EEPROM emulation tables for user credentials, while the watchdog timer resets the panel on firmware lockup to keep the alarm loop alive. OTP also prevents trivial firmware extraction from salvaged parts, an anti-tamper plus for entry-level panels. Pair with a 32.768 kHz crystal for time-of-day scheduling.
Recommended
Battery-Powered Toys and Consumer Gadgets
Cost-sensitive consumer toys, novelty gadgets, and educational kits use the PIC16C55A-20I/SP for sound generation, LED sequencing, and motor PWM at a sub-dollar BOM. The low pin count and small code footprint fit single-function devices, and the OTP memory prevents reverse engineering of proprietary sound patterns. Operating from a regulated 5V rail the part pairs with 4xAA alkaline packs or USB-derived 5V, and the SPDIP-28 through-hole package eases hand assembly in low-volume production. Designers should add a brown-out circuit since the MCU lacks an internal BOR.
Recommended
Hobby and Education Development Boards
Universities and maker communities build PIC16C5X training boards around the PIC16C55A-20I/SP because its 12-bit instruction set is small enough to teach in a single semester yet powerful enough to demonstrate timers, interrupts, and I/O multiplexing. The SPDIP-28 package fits standard 0.1 inch pitch breadboards and ZIF sockets, and OTP programming via the MPLAB PM3 reinforces the link between assembly source and physical bit patterns. Open-source PIC16C5X assembler tutorials and reference manuals from Microchip support coursework.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55A-20I/SP β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-20I/P | PIC16C55A-20/SP | PIC16C55A-04I/P | PIC16C56A-20I/SP | PIC16C54A-20I/P |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | SPDIP-28 | SPDIP-28 - same | SPDIP-28 - same | SPDIP-28 - same | SPDIP-28 - same | SPDIP-28 - same |
| Program Memory | 768 bytes (512 x 12) OTP | 768 bytes OTP | 768 bytes OTP | 768 bytes OTP | 1K x 12 OTP (+33%) | 512 x 12 OTP (-33%) |
| RAM | 24 bytes | 24 bytes | 24 bytes | 24 bytes | 24 bytes | 25 bytes (+1) |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 4 MHz (-80%) | 20 MHz | 20 MHz |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C | 0C to +70C (Commercial) | -40C to +85C | -40C to +85C | -40C to +85C |
| I/O Pins | 20 | 20 | 20 | 20 | 20 | 20 |
| Timers | 1 x 8-bit TMR0 | 1 x 8-bit TMR0 | 1 x 8-bit TMR0 | 1 x 8-bit TMR0 | 1 x 8-bit TMR0 | 1 x 8-bit TMR0 |
| Unit Price @ 1pc (USD, 2026-09-16) | 4.86 | Similar (sister packaging) | Slightly lower (commercial temp) | Lower (slower speed grade) | Slightly higher (larger memory) | Lower (smaller memory) |
Key Differentiators
- 768 bytes of OTP memory - the largest in the PIC16C5X baseline family alongside PIC16C55 siblings (vs PIC16C54A-20I/P)
- Industrial temperature range -40C to +85C for harsh environments (vs PIC16C55A-20/SP)
- 20 MHz max clock for fast bit-banging and timing-critical control loops (vs PIC16C55A-04I/P)
- Pin-compatible upgrade path to PIC16C56A for more code without PCB rework (vs PIC16C56A-20I/SP)
Design Notes
The PIC16C55A-20I/SP requires a regulated 4.5 V to 5.5 V supply on VDD (pin 1). Decouple VDD with a 100 nF ceramic capacitor placed within 5 mm of the supply pin plus a 10 uF tantalum or aluminum bulk capacitor at the board entry point. The MCU does not include an internal brown-out reset, so an external voltage supervisor (e.g. MCP100 or equivalent) is recommended if VDD rise time is slow or if the application must recover from momentary sags. Avoid switching noise from relay coils by placing reverse-biased flyback diodes directly across inductive loads.
Because the PIC16C55A is OTP (one-time-programmable), firmware bugs cannot be patched in the field - every code revision requires a new MCU on every board. Maintain a stable firmware revision and lock the source with the MPLAB PM3 before production. The device has no in-circuit debugger (ICD) header; bring out VDD, VSS, MCLR, OSC1, and OSC2 to test pads so a clip-on programmer or logic analyzer can be attached during bench bring-up. Configure the watchdog timer with a sufficiently long prescaler so that legitimate slow loops do not cause unintended resets.
Route the oscillator traces (OSC1/OSC2) as short as possible and keep them away from high-current switching traces and I/O pins that drive relays. Place the crystal or resonator within 5 mm of OSC1 and OSC2 and ground its case to a quiet ground island. Decouple each VDD pin (one on the 28-pin SPDIP) with a local 100 nF capacitor. The MCLR pin must be pulled high with a 10 kohm resistor and a 100 nF capacitor to VDD for power-on-reset timing per Microchip baseline MCU recommendations.
Estimated: The PIC16C55A-20I/SP in SPDIP-28 has a theta_JA of approximately 60 C/W on a 2-layer test board with still air. At maximum 20 MHz clock with all 20 I/O pins toggling CMOS loads, the part dissipates well under 100 mW, so junction temperature rise above ambient is < 6 C - no heatsink is required. In enclosed enclosures above 60 C ambient, derate I/O drive current to 10 mA per pin or use external buffers to keep junction temperature within the -40C to +85C spec.
Compliance Information
RoHS compliant per Microchip product page. Not AEC-Q100 qualified - use Flash-based PIC16F automotive parts for AEC-Q100 applications. REACH SVHC declaration available on Microchip compliance portal.
