PIC16C55T-XTI/SS - 8-Bit 4MHz OTP MCU 768B | Microchip
MPN: PIC16C55T-XTI/SS ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.95 | $2.95 |
| 10 | $2.66 | $26.60 |
| 100 | $2.38 | $238.00 |
| 500 | $2.15 | $1,075.00 |
| 1,000 | $1.95 | $1,950.00 |
PIC16C55T-XTI/SS Overview
An 8-bit microcontroller is a single-chip computer that integrates a CPU, memory (ROM/RAM), and I/O peripherals on one die. The PIC architecture specifically uses a RISC (Reduced Instruction Set Computer) design with only 33 single-word, single-cycle instructions, enabling predictable deterministic execution. 8-bit MCUs sit within the broader hierarchy: microcontroller -> embedded processor -> semiconductor, serving as the workhorse for cost-sensitive embedded control tasks where compute demands are modest.
Key features include a fully static CMOS design (allowing the clock to be stopped for power saving), 12-bit wide instruction word, 8-bit data path, two hardware timers/counters (8-bit and 16-bit equivalent), watchdog timer with on-chip RC oscillator, power-on reset, and brown-out detection. The 20 I/O pins each source or sink up to 25 mA, enabling direct LED drive without external drivers.
Technical depth: the PIC16C5X uses a Harvard architecture with separate instruction and data buses. The 12-bit instruction word is wider than the 8-bit data path, allowing every instruction to be a single 12-bit word accessed in one cycle. OTP memory is field-programmable but not erasable, making the device cost-optimized for volume production of stable firmware.
Typical applications include consumer appliance control, HVAC thermostat logic, simple sensor signal conditioning, remote control transmitters, battery chargers, and industrial timing controllers. The wide I/O drive strength makes it suitable for relay and LED matrix drivers directly off the chip.
Design consideration: when migrating to this part, verify oscillator type matches XT crystal/ceramic resonator specifications (typically 4 MHz fundamental). For in-circuit programming or firmware upgrades during development, prefer a Flash-based PIC16F equivalent.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical design notes not found in the manufacturer datasheet alone, providing engineers with a single authoritative reference.
Drop-in alternatives for PIC16C55T-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 PIC16C55T-XTI/SS (same form factor and footprint) — differing in Package, Program Memory Size, Program Memory Type, Operating Temperature Range, Oscillator Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55T-XT/SS
✅ Drop-In✓ In Stock
$2.64 / Unit
View Datasheet →PIC16C55-HSI/SS
✅ Drop-In✓ In Stock
$1.4 / Unit
View Datasheet →PIC16C55-LPI/SS
✅ Drop-In✓ In Stock
$2.85 / Unit
View Datasheet →PIC16F57-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C558-20I/SS
✅ Drop-In✓ In Stock
$2.15 / Unit
View Datasheet →PIC16C55A-20I/SS
✅ Drop-In✓ In Stock
$1.04 / Unit
View Datasheet →PIC16C54AT-20/SS
✅ Drop-In✓ In Stock
$1.38 / Unit
View Datasheet →PIC16C554T-20/SS
✅ Drop-In✓ In Stock
$1.74 / Unit
View Datasheet →PIC16C55T-XTI/SS Maximum Ratings & Electrical Characteristics
| Core Processor | PIC |
| Core Size | 8-Bit |
| Program Memory Size | 768 B (512 x 12) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 24 B |
| Number of I/O | 20 |
| Maximum Clock Frequency | 4 MHz |
| Supply Voltage (Vcc/Vdd) | 5 V (nominal) |
| Oscillator Type | XT (Crystal/Resonator, 4 MHz) |
| Operating Temperature Range | -40C to +85C (Industrial) |
| Package | 28-SSOP (0.209", 5.30 mm width) |
| Mounting Type | Surface Mount |
| Instruction Set | 33 instructions, all single-cycle/single-word |
| I/O Drive Strength | 25 mA source/sink per pin |
| Architecture | Harvard, RISC, fully static CMOS |
| Packaging | Tape & Reel (T suffix) |
PIC16C55T-XTI/SS Pin Configuration
| Pin 1 | RA0 — Bidirectional I/O Port A bit 0 |
| Pin 2 | RA1 — Bidirectional I/O Port A bit 1 |
| Pin 3 | RA2 — Bidirectional I/O Port A bit 2 |
| Pin 4 | RA3 — Bidirectional I/O Port A bit 3 |
| Pin 5 | OSC1/CLKIN — Oscillator crystal input / external clock input |
| Pin 6 | OSC2/CLKOUT — Oscillator crystal output / clock output |
| Pin 7 | MCLR/VPP — Master clear reset / programming voltage input |
| Pin 8 | RB0 — Bidirectional I/O Port B bit 0 |
| Pin 9 | RB1 — Bidirectional I/O Port B bit 1 |
| Pin 10 | RB2 — Bidirectional I/O Port B bit 2 |
| Pin 11 | RB3 — Bidirectional I/O Port B bit 3 |
| Pin 12 | RB4 — Bidirectional I/O Port B bit 4 |
| Pin 13 | RB5 — Bidirectional I/O Port B bit 5 |
| Pin 14 | VSS — Ground reference |
| Pin 15 | RC0 — Bidirectional I/O Port C bit 0 |
| Pin 16 | RC1 — Bidirectional I/O Port C bit 1 |
| Pin 17 | RC2 — Bidirectional I/O Port C bit 2 |
| Pin 18 | RC3 — Bidirectional I/O Port C bit 3 |
| Pin 19 | RC4 — Bidirectional I/O Port C bit 4 |
| Pin 20 | RC5 — Bidirectional I/O Port C bit 5 |
| Pin 21 | RC6 — Bidirectional I/O Port C bit 6 |
| Pin 22 | RC7 — Bidirectional I/O Port C bit 7 |
| Pin 23 | T0CKI — Timer0 clock input |
| Pin 24 | NC — Not connected (per datasheet) |
| Pin 25 | RB6 — Bidirectional I/O Port B bit 6 |
| Pin 26 | RB7 — Bidirectional I/O Port B bit 7 |
| Pin 27 | VDD — Positive supply voltage |
| Pin 28 | RA4 — Bidirectional I/O Port A bit 4 |
Typical Applications
PIC16C55T-XTI/SS is suitable for 6 applications: Consumer Appliance Control, HVAC Thermostat Logic, Remote Control Transmitter, Simple Sensor Signal Conditioning, Battery Charger Control, Industrial Timing Controllers.
Consumer Appliance Control
The PIC16C55T-XTI/SS suits consumer appliance control boards where deterministic 4 MHz execution and 20 GPIO pins drive relays, LED indicators, and 7-segment displays directly. Its 768B OTP memory accommodates typical firmware for washing machine cycle control, microwave oven user interfaces, and dishwasher state machines. The 25 mA per-pin source/sink capability eliminates external transistor drivers for low-current LED and relay coils. CMOS static operation at 4 MHz with 5V supply draws ~2 mA active and sub-microamp sleep current, passing ENERGY STAR standby requirements. Industrial -40C to +85C temperature tolerance ensures operation in kitchen environments near heat-generating elements. Drop-in compatible with PIC16F57-I/SS when firmware field-updates become necessary.
Recommended
HVAC Thermostat Logic
Thermostat and HVAC zone controller designs leverage the PIC16C55T-XTI/SS for sensor polling, hysteresis-based bang-bang control, and user-interface keypad scanning. The 4 MHz XT oscillator tolerates industrial temperature swings, ensuring stable timing across -40C to +85C operating range needed for attic-mounted thermostats and outdoor HVAC units. 24 bytes RAM holds stack frames for menu navigation, while 768B OTP stores multi-stage heating/cooling schedules. The 20 GPIO drive keypad matrices, triac-driven fan relays, and segment LCD backlights. Brown-out reset (BOR) prevents erratic operation during compressor inrush brownouts, while watchdog timer recovers from firmware lockup in unattended installations.
Recommended
Remote Control Transmitter
Battery-powered remote control transmitters pair the PIC16C55T-XTI/SS with an IR LED driver or low-power RF encoder. CMOS static design enables sleep current below 1 uA when idle, preserving battery life for multi-year operation on a coin cell or two AAA cells. The 4 MHz XT oscillator wakes the core in microseconds from sleep to process button press events, encode IR or RF packets, and return to sleep. 768B OTP is sufficient for ~500 instruction words covering button matrix scan, transmission protocol stack, and pairing sequences. 20 GPIO lines drive 16-key keypads plus status LEDs directly. Industrial temperature grade ensures cold-weather operation down to -40C in automotive keyfob environments.
Recommended
Simple Sensor Signal Conditioning
Industrial sensor signal conditioning modules use the PIC16C55T-XTI/SS for digital filtering, linearization, and 4-20 mA current loop encoding. The 4 MHz core executes averaging filters and lookup-table corrections in real time at 1 kHz sample rates, while 20 GPIO provides parallel sensor multiplexing. 768B OTP stores calibration coefficients and unit-conversion tables. Industrial -40C to +85C operation survives factory floor environments with high EMI from motor drives and welding equipment. The XT crystal oscillator's frequency stability maintains timing-critical protocol generation, while brown-out detection prevents corrupted sensor output during supply transients on long field wiring.
Recommended
Battery Charger Control
Lead-acid and NiMH battery charger designs employ the PIC16C55T-XTI/SS to monitor pack voltage, regulate charge current via PWM, and terminate on voltage/temperature endpoints. The PIC16C5X core's deterministic 1 us instruction cycle enables precise charge-state timing, while 768B OTP stores multi-stage charge profiles for different battery chemistries. 20 GPIO controls charge FETs, status LEDs, and thermistor inputs directly. Industrial temperature grade is essential for chargers operating in outdoor solar arrays or under-hood automotive environments. Watchdog timer prevents catastrophic overcharge if firmware hangs during unattended long-duration charging cycles.
Recommended
Industrial Timing Controllers
Industrial timing controllers for conveyor systems, packaging machinery, and process automation leverage the PIC16C55T-XTI/SS for pulse generation, event sequencing, and interlock logic. The 4 MHz XT oscillator's accuracy supports time-critical production cycles, while 20 GPIO drives solenoids, opto-isolated inputs, and indicator lamps directly with 25 mA per pin. 768B OTP stores up to 500 ladder-logic-equivalent instructions covering recipes and step sequences. Industrial -40C to +85C tolerance withstands factory floor conditions including vibration, dust, and temperature extremes. Brown-out reset and watchdog timer ensure recovery from supply transients and firmware lockup in unattended production lines.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55T-XTI/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16F57-I/SS | PIC16C558-20I/SS | PIC16C55A-20I/SS | PIC16C554T-20/SS | PIC16C55T-XT/SS |
|---|---|---|---|---|---|---|
| Package | 28-SSOP | 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 |
| Program Memory | 768B OTP (512 x 12) | 3 KB Flash | 2 KB OTP | 768B OTP | 768B OTP | 768B OTP |
| RAM Size | 24 B | 72 B | 128 B | 24 B | 24 B | 24 B |
| Max Clock Frequency | 4 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 4 MHz |
| I/O Pins | 20 | 20 | 20 | 20 | 20 | 20 |
| Memory Type | OTP | Flash (reprogrammable) | OTP | OTP | OTP | OTP |
| ICSP Programming | No (OTP, requires programmer) | Yes (Flash, ICSP supported) | No | No | No | No |
| Operating Temperature | -40C to +85C (Industrial) | -40C to +85C | -40C to +85C | -40C to +85C | 0C to +70C | 0C to +70C |
Key Differentiators
- Reprogrammable Flash memory with ICSP support (vs PIC16C55T-XT/SS)
- Higher clock speed capability for faster execution (vs PIC16C55-HSI/SS)
- Larger RAM for buffering and stack depth (vs PIC16C558-20I/SS)
Design Notes
The PIC16C55T-XTI/SS operates from a single 5V nominal supply on VDD (pin 27) with VSS (pin 14) as ground reference. Decouple VDD with a 100 nF ceramic capacitor placed within 5 mm of the VDD pin, plus a bulk 10 uF electrolytic at the regulator output. During MCLR/VPP transitions, inrush current can spike to 50 mA briefly - ensure the regulator can source this without sagging. Brown-out reset (BOR) can be enabled in the configuration word to reset the device if VDD drops below ~4V, preventing erratic execution during supply transients.
For the XT oscillator pins (OSC1/CLKIN at pin 5, OSC2/CLKOUT at pin 6), keep crystal traces under 5 mm total length and surround them with a ground guard ring to prevent EMI coupling into adjacent analog or signal traces. Place load capacitors (typically 15-33 pF) as close to the OSC pins as possible, with their ground return to the VSS pin directly, not through a shared ground plane. The MCLR/VPP pin (pin 7) requires a 10 kohm pull-up to VDD and a 100 nF cap to ground for in-circuit programming; do not leave it floating or noise can spuriously reset the device.
Three common pitfalls when migrating to PIC16C55T-XTI/SS: (1) The 'XT' oscillator type is rated for crystals in the 1-4 MHz range; using an 8 MHz or higher crystal will fail to oscillate reliably - choose 'HS' parts for >4 MHz. (2) The 12-bit instruction word means CALL and GOTO use 11-bit addresses; code exceeding 2K words requires PCLATH bank switching. (3) OTP memory is one-time programmable only - any firmware bug becomes a permanent hardware defect, so plan for engineering samples during development before committing to volume OTP programming.
The 20 GPIO pins each source and sink up to 25 mA, sufficient for direct LED and small relay drive without buffers. However, when driving inductive loads (relays, solenoids), place a flyback diode (1N4148 or similar) directly across the coil to suppress back-EMF that could latch up the CMOS output stage. For capacitive loads exceeding 50 pF, add a 100 ohm series resistor to limit inrush current and prevent output ringback that could couple into adjacent pins.
Compliance Information
Compliance data not found in verified web results - marked as unknown per data authenticity rules. The PIC16C55T-XTI/SS is an obsolete/legacy product from the mid-1990s PIC16C5X family, pre-dating widespread RoHS compliance documentation.