PIC16C55-XT/SO - 8-Bit 4MHz OTP MCU 20 I/O | Microchip | SOIC-28
MPN: PIC16C55-XT/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.95 | $3.95 |
| 10 | $3.55 | $35.50 |
| 100 | $3.05 | $305.00 |
| 500 | $2.65 | $1,325.00 |
| 1,000 | $2.3 | $2,300.00 |
PIC16C55-XT/SO Overview
What is an 8-bit microcontroller? An 8-bit microcontroller is a single-chip computer that uses an 8-bit-wide data path and executes instructions drawn from on-chip program memory, exposing digital and sometimes analog peripherals for embedded control tasks. The PIC16C5X family sits at the low end of the 8-bit MCU hierarchy - below 16-bit and 32-bit controllers - and is positioned within the broader category of microcontrollers (MCU), embedded processors, and finally integrated circuits. This class of device is optimized for cost-sensitive, deterministic, low-power control applications where 32-bit processing power would be wasted.
The PIC16C55-XT/SO features a 12-bit-wide instruction word with an 8-bit-wide data path, two levels of hardware stack, seven or eight special-function hardware registers, direct/indirect/relative addressing modes, and an 8-bit real-time clock/counter (TMR0). Program memory is one-time programmable (OTP) EPROM, which means each device can be programmed only once - making the part ideal for high-volume production runs where reprogramming is unnecessary. The 20 I/O pins each source or sink up to 25 mA, sufficient to drive LEDs, relays, and small solenoids directly without buffering.
Typical applications span white goods and appliance controls, simple sensor interfaces, LED display drivers, automotive interior modules (where conditions allow), low-end remote controls, and battery-powered instruments. The device is supported by Microchip's MPLAB development ecosystem, including the MPLAB PM3 universal device programmer for production programming and the original PIC16C5X assembly language toolchain.
When designing with the PIC16C55-XT/SO, account for the OTP memory constraint by planning firmware revisions carefully and keeping engineering samples for development. Ensure the XT oscillator's crystal or resonator load capacitors match the manufacturer's specifications, and budget for the 4 MHz instruction-cycle timing margin in real-time control loops.
This page synthesizes distributor pricing, OTP-MCU drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PIC16C55-XT/SO 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 PIC16C55-XT/SO (same form factor and footprint) β differing in Mounting Type, Oscillator Type, Package.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C55T-XT/SO
β Drop-Inβ In Stock
$0.92 / Unit
View Datasheet βPIC16C55T-RC/SO
β Drop-Inβ In Stock
$2.45 / Unit
View Datasheet βPIC16C55-HS/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55A-20I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16F57-I/SO
β Drop-Inπ Reference alternative (not in catalog)
PIC16C55-XT/SO Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC |
| Family | PIC16C5X |
| Data Bus Width | 8 bit |
| Instruction Word Width | 12 bit |
| Maximum CPU Frequency | 4 MHz |
| Program Memory Size | 768 B (512 x 12 words) |
| Program Memory Type | OTP EPROM |
| RAM Size | 24 B |
| Number of I/O Pins | 20 |
| I/O Pin Current (source/sink) | 25 mA per pin |
| Timers | 8-bit TMR0 (1) |
| Hardware Stack Depth | 2 levels |
| Oscillator Type | XT (crystal/resonator, 4 MHz) |
| Package | 28-SOIC (SO) - 7.50 mm body width |
| Mounting Type | Surface Mount |
PIC16C55-XT/SO Pin Configuration
| Pin 1 | RA2 β Bidirectional I/O port A bit 2 |
| Pin 2 | RA3 β Bidirectional I/O port A bit 3 |
| Pin 3 | T0CKI β Timer0 clock input / RA4 |
| Pin 4 | /MCLR β Master clear reset input (active low) |
| Pin 5 | VSS β Ground reference |
| Pin 6 | OSC1 β Oscillator input (XT crystal) |
| Pin 7 | OSC2 β Oscillator output (XT crystal) |
| Pin 8 | RC0 β Bidirectional I/O port C bit 0 |
| Pin 9 | RC1 β Bidirectional I/O port C bit 1 |
| Pin 10 | RC2 β Bidirectional I/O port C bit 2 |
| Pin 11 | RC3 β Bidirectional I/O port C bit 3 |
| Pin 12 | RC4 β Bidirectional I/O port C bit 4 |
| Pin 13 | RC5 β Bidirectional I/O port C bit 5 |
| Pin 14 | RC6 β Bidirectional I/O port C bit 6 |
| Pin 15 | RC7 β Bidirectional I/O port C bit 7 |
| Pin 16 | VSS β Ground reference (second VSS pin) |
| Pin 17 | RB0 β Bidirectional I/O port B bit 0 |
| Pin 18 | RB1 β Bidirectional I/O port B bit 1 |
| Pin 19 | RB2 β Bidirectional I/O port B bit 2 |
| Pin 20 | RB3 β Bidirectional I/O port B bit 3 |
| Pin 21 | RB4 β Bidirectional I/O port B bit 4 |
| Pin 22 | RB5 β Bidirectional I/O port B bit 5 |
| Pin 23 | RB6 β Bidirectional I/O port B bit 6 |
| Pin 24 | RB7 β Bidirectional I/O port B bit 7 |
| Pin 25 | VDD β Positive supply voltage |
| Pin 26 | VDD β Positive supply voltage (second VDD pin) |
| Pin 27 | RA0 β Bidirectional I/O port A bit 0 |
| Pin 28 | RA1 β Bidirectional I/O port A bit 1 |
Typical Applications
PIC16C55-XT/SO is suitable for 6 applications: White Goods and Appliance Control, LED Display and Signage Drivers, Remote Control and IR Transmitter Systems, Automotive Interior Accessory Modules, Battery-Powered Sensor Interfaces, Educational and Hobbyist Embedded Training.
White Goods and Appliance Control
The PIC16C55-XT/SO fits white-goods appliance control applications because its 20 digital I/O pins with 25 mA source/sink capability directly drive relay coils, triac gates, and LED indicators without external buffers. The 4 MHz CPU clock provides sufficient throughput for keypad scanning, timer sequencing, and basic sensor monitoring used in washing machines, dishwashers, and microwave ovens. The OTP memory architecture keeps per-unit cost low in mass-production runs where firmware is finalized, and the 28-SOIC package fits within the compact control boards typical of modern appliances.
Recommended
LED Display and Signage Drivers
The PIC16C55-XT/SO is well-suited to LED display and signage drivers because each of its 20 I/O pins can source or sink 25 mA, enough to drive common-cathode or common-anode LED matrices directly or via simple transistor arrays. The 4 MHz instruction rate supports multiplexed scanning of 7-segment or dot-matrix displays at refresh rates that avoid visible flicker. The 768-byte OTP program memory accommodates fixed message sequences and basic animation tables, and the 28-SOIC surface-mount package integrates cleanly into compact driver PCBs behind retail signage and channel-letter displays.
Recommended
Remote Control and IR Transmitter Systems
The PIC16C55-XT/SO powers low-cost IR remote controls and wireless transmitter systems because the 8-bit core and 4 MHz clock generate accurate 38 kHz carrier waveforms for IR modulation with negligible timing drift. The 20 I/O pins handle matrix keypads up to 4x4 plus status LEDs, and TMR0 provides interrupt-driven key debouncing and timing. The OTP memory stores fixed command codes without field-reprogramming risk, keeping unit cost low. The 28-SOIC package fits inside slim remote-control enclosures alongside IR LEDs and 3 V coin-cell battery holders.
Recommended
Automotive Interior Accessory Modules
The PIC16C55-XT/SO fits automotive interior accessory modules - such as dome-light controllers, seat-heater switches, and accessory delay timers - because the 20 I/O pins switch 12 V automotive loads through external MOSFETs or relays, and the deterministic 8-bit RISC core produces predictable timing for delay-off and pulse-width modulation functions. Designers must observe automotive temperature and EMI conditions; for under-hood or AEC-Q100 applications, migrate to the automotive-qualified PIC16F57 or PIC18 series. The 28-SOIC package mounts on through-hole-friendly lead frames with hand-solderable pads during prototyping.
Recommended
Battery-Powered Sensor Interfaces
The PIC16C55-XT/SO suits battery-powered sensor interface modules because the PIC16C5X family supports low-power SLEEP modes with the XT oscillator gated off, drawing microamp-level standby current suitable for multi-year battery life on 2x AA cells. The 24-byte RAM holds recent sensor samples and the 8-bit TMR0 wakes the part at programmable intervals to read temperature, humidity, or contact-closure sensors on the 20 available I/O pins. The OTP memory avoids accidental field reprogramming that could corrupt long-life sensor deployments.
Recommended
Educational and Hobbyist Embedded Training
The PIC16C55-XT/SO is widely used in educational and hobbyist embedded training because its 28-SOIC package fits DIP-adapter boards for breadboarding, and the PIC16C5X instruction set teaches fundamental 8-bit RISC concepts without the complexity of modern peripherals. Students learn OTP programming workflows, basic I/O toggling, TMR0 interrupt handling, and assembly-level debugging with MPLAB IDE. The 20 I/O pins support a rich set of lab exercises driving LEDs, reading switches, and serial-outputting state. For modern curricula, instructors increasingly substitute PIC16F57-I/SO for reprogrammability, but PIC16C55 remains in legacy training kits.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55-XT/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55T-XT/SO | PIC16C55T-RC/SO | PIC16C55-HS/SO | PIC16C55A-20I/SO | PIC16F57-I/SO |
|---|---|---|---|---|---|---|
| Package | 28-SOIC (SO) | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same | 28-SOIC (SO) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Memory Type | OTP EPROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | OTP EPROM (768 B) | Flash (3 KB) |
| Maximum CPU Frequency | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 20 MHz | 20 MHz |
| Oscillator Type | XT (crystal) | XT (crystal) | RC (low-power) | HS (high-speed crystal) | XT/HS selectable | XT/HS selectable |
| RAM Size | 24 B | 24 B | 24 B | 24 B | 24 B | 72 B |
| Number of I/O Pins | 20 | 20 | 20 | 20 | 20 | 20 |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Active (recommended replacement) |
| Programming Method | OTP (one-time) | OTP (one-time) | OTP (one-time) | OTP (one-time) | OTP (one-time) | Flash ICSP (in-circuit serial programmable) |
Key Differentiators
- PIC16C5X family member with original 8-bit RISC core and OTP EPROM (vs PIC16F57-I/SO)
- Industry-standard XT 4 MHz crystal oscillator option (vs PIC16C55T-RC/SO)
- 20 I/O pins with 25 mA source/sink capability (vs PIC12F1572-I/SN)
Design Notes
PIC16C55-XT/SO uses one-time-programmable (OTP) EPROM. Every silicon unit can be written exactly once - subsequent attempts will fail to program. Engineering teams must finalize firmware completely, verify code on windowed PIC16C55/JW or PIC16F57 emulators, and only then commit production volumes to PIC16C55-XT/SO. Bug fixes in production firmware require a new silicon mask revision or migration to flash-based PIC16F57-I/SO, which adds weeks to months of lead time.
The XT oscillator option supports fundamental-mode crystals or ceramic resonators from approximately 1 MHz to 4 MHz. Load capacitor values must be calculated per the crystal manufacturer's CL specification and total stray capacitance: CL = (C1 x C2) / (C1 + C2) + Cstray. Typical CL of 15-22 pF yields C1 = C2 = 27-33 pF. Excessive load capacitance prevents oscillation startup; insufficient capacitance shifts frequency. Series resistance of 100-330 ohm may be required with low-gain crystals to prevent overdrive.
PIC16C55-XT/SO VDD range is approximately 2.0 V to 6.25 V across commercial temperature grades. Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the VDD pins (pins 25 and 26), and add a bulk 10 uF tantalum or aluminum capacitor near the MCU supply entry point. The /MCLR pin (pin 4) requires a 10 kohm pull-up to VDD; if not driven by an external reset supervisor, add a 10 uF capacitor and 10 kohm resistor for a power-on-reset delay.
The 28-SOIC package has 1.27 mm pin pitch and a 7.50 mm body width. Reserve at least 5 mm of copper clearance around the package for probe access during bench debugging. Route all 20 I/O traces on the top layer or inner layer with continuous ground plane on the opposite side. Keep oscillator traces (OSC1, OSC2) short and guarded by ground copper to minimize EMI pickup. Avoid routing high-speed switching signals under or adjacent to the oscillator traces.
PIC16C55-XT/SO has no internal thermal shutdown - the part relies on its low quiescent current (typically < 2 mA active, < 1 uA sleep) to keep junction temperature within safe limits. At maximum 4 MHz operation with all 20 I/O pins sourcing 25 mA into grounded loads, total package dissipation can approach 500 mW. The 28-SOIC has theta_JA of approximately 80 C/W on a 1 oz 4-layer PCB, allowing sustained operation up to 70 C ambient before derating becomes necessary.
Compliance Information
RoHS, REACH, lead-free, and halogen-free status were not present in the verified web data for this obsolete part. AEC-Q100 not qualified - PIC16C55-XT/SO is a commercial-grade part. Contact Microchip or authorized distributors for compliance documentation before volume procurement.
