PIC16C55-XTI/SS - 8-bit OTP MCU 768B 24 RAM 20 I/O SSOP28
MPN: PIC16C55-XTI/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.5252 | $5.53 |
| 10 | $4.97 | $49.70 |
| 100 | $3.92 | $392.00 |
| 500 | $3.18 | $1,590.00 |
| 1,000 | $2.74 | $2,740.00 |
PIC16C55-XTI/SS Overview
An 8-bit microcontroller (MCU) is a small single-chip computer built around an 8-bit data path, integrating a CPU, program memory, data RAM, I/O peripherals, and timers in one package. MCUs sit below microprocessors (MPUs) in the system hierarchy and serve as the embedded decision-makers in appliances, sensors, motor controllers, and many other everyday devices. The PIC16C5X family belongs to the original baseline PIC architecture, sharing the same 12-bit wide instruction word across PIC16C54, PIC16C55, PIC16C56, and PIC16C57 devices, with each successive part offering progressively larger program memory.
Key features of the PIC16C55-XTI/SS include a 12-bit instruction set with 8-bit data path, two-level deep hardware call stack, direct/indirect/relative addressing modes, an 8-bit real-time clock/counter (TMR0) with programmable prescaler, and a watchdog timer for reliable unattended operation. The device runs from a 2.5V to 6.25V supply (industrial extended range per PIC16C5X datasheet), supports up to 4 MHz external clock input, and delivers 33 single-word instructions with two-cycle conditional branches.
Architecturally, the PIC16C55 uses Harvard-style separate program and data buses, allowing instruction fetch and operand read to occur in a single oscillator cycle. This gives the part a 1 MIPS rating at 4 MHz clock. The CMOS process delivers low power consumption (typical < 2 mA active at 5V/4 MHz, < 1 uA standby) suitable for battery-influenced designs. The 20 I/O pins can source/sink up to 20-25 mA per pin, allowing direct LED drive and small-signal transistor switching.
Typical applications for PIC16C55-XTI/SS include simple appliance controllers (coffee makers, fans, blenders), automotive interior accessories, low-end sensor interface boards, educational microcontroller learning kits, and hobbyist / replacement-board designs where the classic PIC16C5X instruction set is already embedded in the firmware. Because the part ships as OTP, it is best suited for low- to medium-volume production runs where mask-ROM cost cannot be justified.
When designing with the PIC16C55-XTI/SS, pay close attention to the OTP programming window: once programmed, the bit cannot be erased, so prototype code must be burned into ceramic-windowed PIC16C55/JW parts first. The industrial-temperature XTI grade enables field deployment in unheated enclosures but limits the maximum oscillator to 4 MHz - do not substitute XT or HS grade parts without re-validating timing margins. For new designs, Microchip recommends the flash-based PIC16F54 or PIC16F57 as modern drop-in successors with in-circuit programmability.
This page synthesizes distributor pricing, parametric drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PIC16C55-XTI/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 PIC16C55-XTI/SS (same form factor and footprint) — differing in Program Memory Size, Package, Program Memory Type, Oscillator Type, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55-XTE/SS
✅ Drop-In✓ In Stock
$1.94 / Unit
View Datasheet →PIC16C55A-XTI/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C55T-XTI/SS
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →PIC16C55T-HSI/SS
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C55-LPI/SS
✅ Drop-In✓ In Stock
$2.85 / Unit
View Datasheet →PIC16C55-HSI/SS
✅ Drop-In✓ In Stock
$1.4 / Unit
View Datasheet →PIC16C558-20/SS
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C55-XTI/SS Maximum Ratings & Electrical Characteristics
| Family | PIC16C5X (PIC16C55) |
| Core | 8-bit PIC RISC |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 bytes (512 x 12-bit words) |
| Data RAM | 24 bytes |
| Maximum Clock Frequency | 4 MHz |
| Instruction Set Width | 12-bit wide instructions, 8-bit data path |
| Number of I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0) with programmable prescaler |
| Watchdog Timer | Yes (on-chip) |
| Hardware Stack | 2-level deep |
| Supply Voltage Range | 2.5 V to 6.25 V |
| Operating Temperature Range | -40 C to +85 C (Industrial) |
| Package | 28-pin SSOP (5.30 mm body width) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (per distributor listings) |
PIC16C55-XTI/SS Pin Configuration
| Pin 1 | RA0 — Port A bit 0 (digital I/O) |
| Pin 2 | RA1 — Port A bit 1 (digital I/O) |
| Pin 3 | RA2 — Port A bit 2 (digital I/O) |
| Pin 4 | RA3 — Port A bit 3 (digital I/O) |
| Pin 5 | RB0/INT — Port B bit 0 / external interrupt input |
| Pin 6 | RB1 — Port B bit 1 (digital I/O) |
| Pin 7 | RB2 — Port B bit 2 (digital I/O) |
| Pin 8 | RB3 — Port B bit 3 (digital I/O) |
| Pin 9 | RB4 — Port B bit 4 (digital I/O) |
| Pin 10 | RB5 — Port B bit 5 (digital I/O) |
| Pin 11 | RB6 — Port B bit 6 (digital I/O) |
| Pin 12 | RB7 — Port B bit 7 (digital I/O) |
| Pin 13 | RC0 — Port C bit 0 (digital I/O) |
| Pin 14 | RC1 — Port C bit 1 (digital I/O) |
| Pin 15 | RC2 — Port C bit 2 (digital I/O) |
| Pin 16 | RC3 — Port C bit 3 (digital I/O) |
| Pin 17 | RC4 — Port C bit 4 (digital I/O) |
| Pin 18 | RC5 — Port C bit 5 (digital I/O) |
| Pin 19 | RC6 — Port C bit 6 (digital I/O) |
| Pin 20 | RC7 — Port C bit 7 (digital I/O) |
| Pin 21 | VSS — Ground reference |
| Pin 22 | VDD — Positive supply voltage |
| Pin 23 | OSC1/CLKIN — Oscillator input / external clock input |
| Pin 24 | OSC2/CLKOUT — Oscillator output / clock output |
| Pin 25 | T0CKI — Timer 0 clock input |
| Pin 26 | /MCLR — Master clear (active-low reset) / VPP programming voltage |
| Pin 27 | NC — Not connected (per datasheet) |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
PIC16C55-XTI/SS is suitable for 7 applications: Appliance Control Boards, Automotive Interior Accessories, Low-End Sensor Interface Boards, Educational Microcontroller Kits, Hobbyist Replacement Boards, Industrial Simple Logic Replacement, Low-Volume Production Controllers.
Appliance Control Boards
The PIC16C55-XTI/SS fits small appliance controllers because it delivers 20 I/O pins at 4 MHz with 768 bytes of OTP program memory - enough for coffee maker, blender, fan, or rice cooker state machines. Its 24-byte RAM supports simple timing counters and button de-bounce without external memory expansion. Industrial -40C to +85C temperature grade lets the same part ship into unheated laundry-room or garage enclosures, while the 20-25 mA per-pin drive directly switches relay coils and indicator LEDs without buffer transistors, cutting BOM cost.
Recommended
Automotive Interior Accessories
The PIC16C55-XTI/SS serves interior automotive accessories such as dome-light timers, simple seat-controller switches, or aftermarket alarm LED indicators. Its 2.5V to 6.25V supply range tolerates cranking transients when paired with proper supply decoupling, and the 4 MHz instruction rate delivers 1 MIPS throughput for input scanning and PWM-style LED dimming. The PIC16C5X family's mature CMOS process gives high EMI immunity for noisy automotive electrical environments, while the SSOP-28 footprint drops onto compact accessory PCBs.
Recommended
Low-End Sensor Interface Boards
The PIC16C55-XTI/SS works well as a low-cost sensor-interface front-end for thermostat keypads, basic security PIR boards, or environmental sensor nodes. Its 8-bit TMR0 with programmable prescaler captures timing pulses from HC-SR04 ultrasonic sensors or counts pulses from flow meters; the 24-byte RAM holds calibration constants and rolling averages. The 20 I/O pins scan up to 4x4 key matrices or drive seven-segment LCD bias networks. Industrial temperature grade supports outdoor and basement deployment without additional thermal protection.
Recommended
Educational Microcontroller Kits
The PIC16C55-XTI/SS is well suited to university and trade-school embedded systems labs teaching classic PIC assembly programming. Its 33-instruction RISC architecture is small enough for students to master in one semester, and the OTP-memory constraint forces good documentation habits that translate to flash-PIC development. The SSOP-28 footprint teaches surface-mount soldering skills, while the 28-SSOP-to-DIP28 adapter board lets students reuse breadboard-friendly breakout carriers. The classic PIC16C5X instruction set is documented in hundreds of textbooks, lowering curriculum cost.
Recommended
Hobbyist Replacement Boards
The PIC16C55-XTI/SS remains a popular choice for restoring legacy hobbyist and amateur-radio projects built around the original PIC16C5X family. Many homebrew QRP radio controllers, antenna rotator interfaces, and ham repeater ID timers shipped with PIC16C55 firmware that is no longer compatible with newer PIC18 or PIC24 instruction sets. The drop-in replacement strategy lets hobbyists rebuild dead boards by ordering PIC16C55-XTI/SS with the same 28-SSOP footprint, same 768-byte OTP memory, and same PIC16C5X instruction set that the original firmware targets.
Recommended
Industrial Simple Logic Replacement
The PIC16C55-XTI/SS replaces discrete 74HC logic gates and small PLDs in industrial sequencers, conveyor zone controllers, and packaging-machine timer boards. With 20 I/O pins, 768 bytes of OTP for state-machine code, and 1 MIPS throughput at 4 MHz, the device replaces a dozen or more TTL packages while adding flexibility to change timing parameters in firmware rather than resistor swaps. The -40C to +85C industrial temperature rating handles factory-floor environments, and the SSOP-28 package fits legacy board footprints during retrofit programs.
Recommended
Low-Volume Production Controllers
The PIC16C55-XTI/SS is ideal for low- to medium-volume production (100-10,000 units) where mask-ROM cost cannot be justified but production-grade reliability is required. The OTP EPROM gives a stable one-time-programmed code image that does not suffer flash-memory bit-rotation issues, while the PIC16C5X family's mature 0.9um CMOS process has long-term production continuity from Microchip. Industrial temperature grade supports unheated cabinet deployment, and the SSOP-28 package supports automated pick-and-place assembly without reel-orientation concerns specific to BGA parts.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55-XTI/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55-XTE/SS | PIC16C55A-XTI/SS | PIC16C55T-XTI/SS | PIC16C55T-HSI/SS | PIC16C55-LPI/SS | PIC16C558-20/SS |
|---|---|---|---|---|---|---|---|
| Package | 28-SSOP | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same | 28-SSOP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Program Memory | 768 bytes OTP | 768 bytes OTP | 768 bytes OTP | 768 bytes OTP | 768 bytes OTP | 768 bytes OTP | 2048 bytes OTP (larger) |
| Data RAM | 24 bytes | 24 bytes | 24 bytes | 24 bytes | 24 bytes | 24 bytes | 128 bytes (larger) |
| Maximum Clock | 4 MHz (XT grade) | 4 MHz (XT grade) | 4 MHz (XT grade) | 4 MHz (XT grade) | 20 MHz (HS grade) | 200 kHz (LP grade) | 20 MHz |
| Operating Voltage | 2.5V - 6.25V | 2.0V - 6.0V (extended) | 2.5V - 6.25V | 2.5V - 6.25V | 2.5V - 6.25V | 2.5V - 6.25V | 2.5V - 6.25V |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM |
Key Differentiators
- Mature industrial-temperature grade with -40C to +85C operating range (vs PIC16C55-XT/SO (commercial grade, 0C to +70C))
- Lower power dissipation at 4 MHz vs higher-clock PIC16C5X HS variants (vs PIC16C55T-HSI/SS (HS grade, 20 MHz))
- Smaller OTP memory footprint than PIC16C558 family at lower cost (vs PIC16C558-20/SS (2048 bytes OTP, 128 bytes RAM))
Design Notes
The PIC16C55-XTI/SS requires a stable 2.5V to 6.25V supply. Place a 100 nF decoupling capacitor as close as possible to the VDD pin (pin 22) with a short ground return to VSS (pin 21). For battery-powered designs, add a 10 uF bulk capacitor near the supply input and a series ferrite bead to suppress ESD and motor noise transients from relay-driven loads on the I/O pins. The /MCLR pin (pin 26) should be pulled up to VDD through a 10 kohm resistor with a 100 nF capacitor to VSS for clean reset behavior.
Because PIC16C55-XTI/SS uses One-Time Programmable (OTP) EPROM, there is no way to erase or rewrite the device once programmed - a single bit error renders the part unusable. Always prototype on windowed PIC16C55/JW parts (with quartz erasure window) or modern flash-based PIC16F54-I/SS before committing to OTP production. Verify all configuration bits (oscillator selection, watchdog enable, code-protect) match your design intent before bulk programming. Programming voltage on /MCLR must follow Microchip's VPP specification from the PIC16C5X datasheet, typically 13V nominal.
When laying out the SSOP-28 footprint for PIC16C55-XTI/SS, follow Microchip's recommended PCB land pattern with 0.025 inch lead pitch and 0.010 inch solder mask expansion. Keep the crystal or resonator within 0.5 inch of pins 23-24 (OSC1/OSC2) to minimize stray capacitance and EMI pickup. Route the /MCLR trace away from high-current switching lines to prevent false resets. Place the VDD decoupling capacitor's ground return via directly to the VSS via, not through a shared ground trace, to avoid supply noise coupling into the reference rail.
Compliance Information
RoHS and lead-free compliance per distributor listings (Heisener, Mouser, AmpHeo, LCSC). Not AEC-Q100 qualified - for automotive safety-critical applications use AEC-Q100 qualified PIC16F1xxx family members. REACH compliance per Microchip product environmental certifications.
