PIC16C55-XT/P - 8-bit 4MHz OTP MCU 20 I/O 28-PDIP | Microchip
MPN: PIC16C55-XT/P ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.95 | $6.95 |
| 10 | $6.12 | $61.20 |
| 100 | $5.32 | $532.00 |
| 500 | $4.68 | $2,340.00 |
| 1,000 | $4.05 | $4,050.00 |
PIC16C55-XT/P Overview
A baseline PIC microcontroller (also written PICmicro) is an 8-bit fully-static, EPROM/ROM-based CMOS MCU family defined by a RISC instruction set with 12-bit-wide instructions and 8-bit-wide data paths. The PIC16C5X line sits at the bottom of Microchip's PIC hierarchy: baseline PIC16C5X -> mid-range PIC16 -> enhanced mid-range PIC16 -> PIC18 -> PIC24 -> dsPIC -> 32-bit PIC32. Baseline PICs use a small instruction set, a single 8-bit accumulator (W), and a limited two-level stack, optimized for cost-sensitive embedded control rather than compute throughput.
Key features of the PIC16C55-XT/P include 33 single-word instructions, two-level hardware stack, direct/indirect/relative addressing modes, power-on reset, power-saving SLEEP mode, watchdog timer with dedicated on-chip RC oscillator, and programmable code protection. The XT speed grade specifies an external crystal/resonator oscillator range of approximately 100 kHz to 4 MHz, and the device operates from 3.0V to 6.0V (per the family datasheet; 4.5-5.5V typical for full-speed operation).
Architecturally, the PIC16C55 uses a Harvard-class memory layout with separate program and data buses, a single working register (W), seven or eight Special Function Registers, and a 7-bit file register map. The 12-bit instruction word yields roughly a 2:1 code compression advantage over comparable CISC 8-bit controllers. There is no hardware multiplier, no interrupt controller, and no in-circuit debugger (ICD) — the baseline family trades features for die size and unit cost.
Typical applications include low-cost consumer appliances, sensor signal conditioning, simple motor/relay control, automotive body controllers, and educational/hobbyist designs that target the classic PIC16C5X pinout. The 28-pin PDIP footprint also enables easy breadboard prototyping and windowed CERDIP emulation variants (such as PIC16C55-JW).
When designing with this part, allocate one I/O pin for MCLR reset, choose the appropriate oscillator mode (XT for standard crystals), and verify the OTP programming procedure against the Microchip programming specification, because OTP parts cannot be reprogrammed or erased after coding.
This page synthesizes distributor pricing, drop-in alternative MPNs, and practical design notes not aggregated on any single distributor or manufacturer page.
Drop-in alternatives for PIC16C55-XT/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 PIC16C55-XT/P (same form factor and footprint) — differing in Package, Timers, Program Memory Type, Operating Temperature, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55A-04I/P
✅ Drop-In✓ In Stock
$1.52 / Unit
View Datasheet →PIC16C55A-20I/P
✅ Drop-In✓ In Stock
$1.6 / Unit
View Datasheet →PIC16C55A-20I/SP
✅ Drop-In✓ In Stock
$3.01 / Unit
View Datasheet →PIC16C55-10I/P
✅ Drop-In✓ In Stock
$2.58 / Unit
View Datasheet →PIC16C55-10/SP
✅ Drop-In✓ In Stock
$2.45 / Unit
View Datasheet →PIC16C55/JW
✅ Drop-In✓ In Stock
$10.4 / Unit
View Datasheet →PIC16C55-XT/P Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit PIC baseline (PIC16C5X) |
| Program Memory | 768 bytes (512 x 12) OTP |
| RAM | 24 bytes |
| Maximum Clock Speed | 4 MHz (XT speed grade) |
| Instruction Word Width | 12 bits |
| Data Path Width | 8 bits |
| Number of Instructions | 33 |
| I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0) |
| Hardware Stack Depth | 2 levels |
| Oscillator Mode | XT (external crystal/resonator, ~100 kHz to 4 MHz) |
| Supply Voltage | 3.0 V to 6.0 V (4.5 V to 5.5 V typical at full speed) |
| Watchdog Timer | Yes, with dedicated on-chip RC oscillator |
| Package | 28-pin PDIP (0.600 inch, 15.24 mm) |
| Program Memory Type | OTP (One-Time Programmable) EPROM |
| Operating Temperature | 0C to +70C (commercial; -40C to +85C industrial variant exists in family) |
| Mounting Type | Through-Hole (DIP) |
| RoHS Status | Compliant (PDIP lead-free finish) |
PIC16C55-XT/P Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 — Bidirectional I/O port A bit 3 |
| Pin 3 | RA4/T0CKI — Bidirectional I/O port A bit 4 / Timer0 clock input |
| Pin 4 | MCLR — Master Clear reset input (active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0/INT — Bidirectional I/O port B bit 0 / external interrupt input |
| Pin 7 | RB1 — Bidirectional I/O port B bit 1 |
| Pin 8 | RB2 — Bidirectional I/O port B bit 2 |
| Pin 9 | RB3 — Bidirectional I/O port B bit 3 |
| Pin 10 | RB4 — Bidirectional I/O port B bit 4 |
| Pin 11 | RB5 — Bidirectional I/O port B bit 5 |
| Pin 12 | RB6 — Bidirectional I/O port B bit 6 |
| Pin 13 | RB7 — Bidirectional I/O port B bit 7 |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 16 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 17 | RA0 — Bidirectional I/O port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O port A bit 1 |
| Pin 19 | RC0 — Bidirectional I/O port C bit 0 |
| Pin 20 | RC1 — Bidirectional I/O port C bit 1 |
| Pin 21 | RC2 — Bidirectional I/O port C bit 2 |
| Pin 22 | RC3 — Bidirectional I/O port C bit 3 |
| Pin 23 | RC4 — Bidirectional I/O port C bit 4 |
| Pin 24 | RC5 — Bidirectional I/O port C bit 5 |
| Pin 25 | RC6 — Bidirectional I/O port C bit 6 |
| Pin 26 | RC7 — Bidirectional I/O port C bit 7 |
| Pin 27 | NC — Not connected (per datasheet) |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
PIC16C55-XT/P is suitable for 6 applications: Low-Cost Consumer Appliance Control, Industrial Sensor Signal Conditioning, Simple Relay and Solenoid Driver Controller, Automotive Body Electronics (Legacy NRND), Educational and Hobbyist Microcontroller Projects, Replacement of Obsolete Legacy 8-bit MCUs.
Low-Cost Consumer Appliance Control
The PIC16C55-XT/P fits low-cost consumer appliance control because its 768-byte OTP memory and 20 I/O pins can directly drive relays, triacs, LEDs, and keypads without external glue logic. Its 4 MHz instruction rate delivers ~1 MIPS, sufficient for simple state-machine timing of washing-machine cycles, microwave ovens, and toaster controllers. The two-level hardware stack limits nested subroutine depth, which is acceptable for flat C-style state machines typical in appliance firmware. The 28-PDIP package enables easy through-hole assembly for high-volume appliance PCBs.
Recommended
Industrial Sensor Signal Conditioning
The PIC16C55-XT/P suits industrial sensor signal conditioning front-ends where its 8-bit ADC-free architecture is paired with external analog front-ends to digitize thermocouple, RTD, or pressure-bridge signals. The 24-byte RAM and 768-byte OTP support small lookup-table linearization routines; the watchdog timer with on-chip RC oscillator enables reliable unattended sensor-node operation. Operating from 3.0V to 6.0V and up to +70C commercial range, the part tolerates industrial enclosure environments while keeping BOM cost minimal for high-channel-count sensor arrays.
Recommended
Simple Relay and Solenoid Driver Controller
The PIC16C55-XT/P drives relays and solenoids directly through its 20-mA capable I/O pins, paired with Darlington arrays like the ULN2003A. Its single TMR0 counter provides timing for PWM-free bang-bang control loops adequate for irrigation valves, vending-machine dispensing, and HVAC damper actuators. The XT oscillator grade supports standard 4 MHz crystals, ensuring deterministic timing for safety interlocks. The 28-PDIP package withstands industrial wiring harness assembly stresses better than SMD alternatives.
Recommended
Automotive Body Electronics (Legacy NRND)
Although NRND, the PIC16C55-XT/P and its automotive-grade sibling PIC16C55A-04I/P still serve automotive body-electronics applications including seat controllers, mirror adjusters, and interior lighting where proven baseline PIC firmware is locked-in. The 20 I/O pins handle multiple switch inputs and load outputs, while the on-chip watchdog timer improves field reliability against supply transients. Designers should migrate to PIC16F family successors for new automotive programs, but existing production runs continue to use this part due to validated firmware investment.
Recommended
Educational and Hobbyist Microcontroller Projects
The PIC16C55-XT/P remains a popular educational platform because its 28-pin PDIP fits standard 0.6-inch breadboards, its 33-instruction RISC architecture is simple enough to teach assembly fundamentals, and its low cost (~$5 in unit quantity) makes it affordable for classroom lab kits. The OTP nature enforces good programming hygiene (one-shot burn-and-test cycle), and the windowed PIC16C55-JW variant supports UV erase and reprogramming for iterative student labs. University microcontroller courses and Arduino-adjacent hobbyists use this part for foundational embedded-systems curricula.
Recommended
Replacement of Obsolete Legacy 8-bit MCUs
The PIC16C55-XT/P is widely used as a drop-in replacement for obsolete 8048/8051, COP8, and Z8-family microcontrollers in legacy industrial controllers, because its 28-PDIP footprint and 20-I/O pin count match several of those older footprints, and its 4 MHz instruction rate is sufficient to emulate slower legacy firmware. Systems with decade-old control boards — including test equipment, elevator controllers, and textile machinery — often migrate to PIC16C55 or PIC16C55A to extend equipment life without PCB redesign. The OTP memory requires careful firmware validation before committing production volumes.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55-XT/P — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55A-04I/P | PIC16C55A-20I/P | PIC16C55A-20I/SP | PIC16C55-10I/P | PIC16C55/JW |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 28-PDIP (0.600 inch) | 28-PDIP (0.600 inch) - same | 28-PDIP (0.600 inch) - same | 28-SPDIP (0.300 inch) - narrower body | 28-PDIP (0.600 inch) - same | 28-Cerdip windowed - same pin pitch, larger body |
| Program Memory | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP | 768 B (512 x 12) OTP | 768 B (512 x 12) windowed UV EPROM |
| Maximum Clock | 4 MHz (XT) | 4 MHz (XT) | 20 MHz (HS) | 20 MHz (HS) | 10 MHz | 4 MHz (XT) |
| Supply Voltage | 3.0 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 2.5 V to 6.0 V | 3.0 V to 6.0 V | 3.0 V to 6.0 V |
| Operating Temperature | 0C to +70C | -40C to +85C (industrial) | -40C to +85C (industrial) | -40C to +85C (industrial) | -40C to +85C (industrial) | 0C to +70C |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Windowed UV-erasable EPROM |
| Lifecycle Status | NRND | Active | Active | Active | NRND | Active (legacy emulator) |
| RoHS Compliant | Yes | Yes | Yes | Yes | Yes | No (ceramic windowed) |
Key Differentiators
- Baseline PIC16C5X core with 33-instruction RISC ISA (vs PIC16C55A-04I/P)
- XT oscillator grade optimized for 4 MHz standard crystals (vs PIC16C55A-20I/P)
- 28-PDIP through-hole package for breadboard prototyping (vs PIC16C55A-20I/SP)
Design Notes
The PIC16C55-XT/P requires a stable VDD between 3.0V and 6.0V with a 100 nF decoupling capacitor placed within 5 mm of the VDD pin (pin 14) and a 10 uF bulk capacitor on the same node. Brown-out behavior is minimal on the original PIC16C55 silicon, so for industrial applications an external voltage supervisor such as MCP100 or MCP102 is recommended to guarantee a clean reset when VDD falls below 2.7V. The MCLR pin (pin 4) should be pulled high through a 10 kohm resistor and decoupled with a 100 nF capacitor to filter noise-induced resets.
Because the PIC16C55 has only a two-level hardware stack, recursive subroutines or deeply nested ISRs will overwrite the return PC and cause firmware malfunction. The baseline PIC16C5X family has no hardware interrupt controller — only the RB0/INT pin external interrupt is supported, and it cannot wake the part from SLEEP in all oscillator modes. OTP parts cannot be reprogrammed: a single programming failure on the OTP die means the entire IC is scrapped, so always validate firmware on a PIC16C55/JW windowed emulator before committing production OTP volume.
Route the XT oscillator traces (OSC1 pin 16, OSC2 pin 15) as short as possible, surrounded by a ground pour, and place the load capacitors (typically 15-33 pF for 4 MHz crystals) within 5 mm of the oscillator pins. Keep switching signal traces (relay drivers, triac outputs on PORTC) at least 5 mm away from the oscillator traces to avoid capacitive injection of noise that can corrupt the system clock. The MCLR trace (pin 4) should be guarded with a ground trace on both sides if the board has high dV/dt switching nodes nearby.
Compliance Information
RoHS compliant per Microchip product page. AEC-Q100 not qualified - automotive designs should migrate to PIC16C55A-04I/P or PIC16F family. PIC16C55/JW (CERDIP windowed) is non-RoHS due to ceramic body.
