PIC16C55-HSI/SO - 8-Bit 20MHz OTP MCU 768B | Microchip 28-SOIC
MPN: PIC16C55-HSI/SO ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.974 | $1.97 |
| 10 | $1.78 | $17.80 |
| 100 | $1.62 | $162.00 |
| 500 | $1.48 | $740.00 |
| 1,000 | $1.35 | $1,350.00 |
PIC16C55-HSI/SO Overview
An 8-bit microcontroller (MCU) is a small computer-on-a-chip containing a CPU, RAM, ROM/EPROM/Flash program memory, I/O ports, and one or more timers on a single die. It belongs to the broader hierarchy: microcontroller -> embedded processor -> semiconductor -> integrated circuit. The PIC16C5X family uses a RISC-style Harvard architecture with separate program and data buses, a 12-bit-wide instruction word, and an 8-bit-wide data path, allowing single-cycle instruction execution on most instructions. This contrasts with 8051-family CISC designs that often need multiple cycles per opcode.
Key differentiating specifications include a 12-bit instruction word (vs 14-bit on PIC16C6X/7X), a two-level hardware stack (vs 8-level on PIC16C6X), 20 I/O pins with high-current sink/source capability, an 8-bit real-time counter/timer (TMR0) with an 8-bit programmable prescaler, and direct/indirect/relative addressing modes for both data and instructions. The PIC16C55 family supports 33 single-word instructions with a 200 ns instruction cycle at 20 MHz oscillator input.
Typical applications for the PIC16C55-HSI/SO include low-cost consumer appliances, automotive body controllers (non-AEC-Q), industrial timer/counter modules, simple sensor conditioning front-ends, remote-control transmitters, and replacement of discrete logic in glue-logic consolidation designs. The 28-SOIC package is suitable for hand-soldered prototypes and automated SMT lines where DIP packages would be too tall.
When designing with the PIC16C55-HSI/SO, remember that OTP parts cannot be re-programmed in-circuit after the window-sealable ceramic package has been exposed to UV - the SOIC version has no erasure window, so code is committed at first programming. For development, use the JW (windowed CERDIP) variant of the same die for iterative code cycles. The device is no longer recommended for new designs (NRND) by Microchip; consider PIC16F54 or PIC16F57 flash-based parts as modern equivalents.
This page synthesizes distributor pricing, drop-in alternatives within the same PIC16C55/PIC16C57 family, and practical design notes not aggregated on a single manufacturer page.
Drop-in alternatives for PIC16C55-HSI/SO — 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-HSI/SO (same form factor and footprint) — differing in Package, Timers, Program Memory Size, Program Memory Type, Core Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C55-HSI/P
✅ Drop-In✓ In Stock
$2.6 / Unit
View Datasheet →PIC16C55AT-20/SO
✅ Drop-In✓ In Stock
$1.45 / Unit
View Datasheet →PIC16C55-10/SO
✅ Drop-In✓ In Stock
$2.49 / Unit
View Datasheet →PIC16F54-I/SO
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C558-20/SO
✅ Drop-In✓ In Stock
$2.05 / Unit
View Datasheet →PIC16C55-HSI/SO Maximum Ratings & Electrical Characteristics
| Family | PIC16C5X |
| Core | 8-bit RISC Harvard |
| Program Memory Type | OTP EPROM |
| Program Memory Size | 768 B (512 x 12 words) |
| Data RAM | 24 B to 32 B |
| Maximum CPU Speed | 20 MHz |
| Instruction Cycle Time | 200 ns at 20 MHz |
| Instruction Word Width | 12 bits |
| I/O Pins | 20 |
| Timers | 1 x 8-bit (TMR0 with 8-bit prescaler) |
| Hardware Stack Depth | 2 levels |
| Number of Instructions | 33 |
| Oscillator Mode | HS (high-speed crystal/ceramic resonator, 20 MHz max) |
| Operating Voltage | 3.0 V to 6.25 V |
| Operating Temperature | -40C to +85C (industrial) |
| Package | 28-pin SOIC (SO, 7.50 mm / 0.295 in width) |
| Mounting Type | Surface Mount |
| RoHS Status | non_compliant (28-SOIC contains SnPb lead finish on legacy parts) |
| Lead-Free Option | No (SnPb finish on SO package) |
PIC16C55-HSI/SO Pin Configuration
| Pin 1 | RA2 — Port A bit 2 (bidirectional I/O) |
| Pin 2 | RA3 — Port A bit 3 (bidirectional I/O) |
| Pin 3 | RA4/T0CKI — Port A bit 4 / TMR0 clock input |
| Pin 4 | MCLR — Master Clear reset (active low) |
| Pin 5 | VSS — Ground reference |
| Pin 6 | OSC1/CLKIN — Oscillator input / external clock in |
| Pin 7 | OSC2/CLKOUT — Oscillator output / clock out (Fosc/4) |
| Pin 8 | RB0 — Port B bit 0 (bidirectional I/O) |
| Pin 9 | RB1 — Port B bit 1 (bidirectional I/O) |
| Pin 10 | RB2 — Port B bit 2 (bidirectional I/O) |
| Pin 11 | RB3 — Port B bit 3 (bidirectional I/O) |
| Pin 12 | RB4 — Port B bit 4 (bidirectional I/O) |
| Pin 13 | RB5 — Port B bit 5 (bidirectional I/O) |
| Pin 14 | RB6 — Port B bit 6 (bidirectional I/O) |
| Pin 15 | RB7 — Port B bit 7 (bidirectional I/O) |
| Pin 16 | RC0 — Port C bit 0 (bidirectional I/O) |
| Pin 17 | RC1 — Port C bit 1 (bidirectional I/O) |
| Pin 18 | RC2 — Port C bit 2 (bidirectional I/O) |
| Pin 19 | RC3 — Port C bit 3 (bidirectional I/O) |
| Pin 20 | RC4 — Port C bit 4 (bidirectional I/O) |
| Pin 21 | RC5 — Port C bit 5 (bidirectional I/O) |
| Pin 22 | RC6 — Port C bit 6 (bidirectional I/O) |
| Pin 23 | RC7 — Port C bit 7 (bidirectional I/O) |
| Pin 24 | VSS — Ground reference (second pin on SOIC) |
| Pin 25 | VDD — Positive supply voltage |
| Pin 26 | RA0 — Port A bit 0 (bidirectional I/O) |
| Pin 27 | RA1 — Port A bit 1 (bidirectional I/O) |
| Pin 28 | NC — Not connected (per datasheet, 28-SOIC variant) |
Typical Applications
PIC16C55-HSI/SO is suitable for 6 applications: Low-Cost Consumer Appliance Control, Automotive Body Electronics (Non-Safety), Industrial Timer and Counter Modules, Remote Control Transmitter, Glue-Logic Replacement / Discrete Logic Consolidation, Sensor Conditioning Front-End.
Low-Cost Consumer Appliance Control
The PIC16C55-HSI/SO fits consumer appliance control because its 768 B OTP memory and 33 single-word instructions are sufficient for fixed-function state machines like washing-machine timers, microwave keypad controllers, and toaster oven mode logic. The 20 MHz CPU clock delivers a 200 ns instruction cycle, which is more than enough to scan 4x4 keypads, debounce mechanical switches, and drive 7-segment or LCD displays in real time at 10 ms refresh. Its 20 I/O pins accommodate up to 20 relays, LEDs, or sensor inputs without external mux. The OTP EPROM locks the firmware permanently after programming, eliminating reprogramming risks in the field.
Recommended
Automotive Body Electronics (Non-Safety)
The PIC16C55-HSI/SO is used in non-safety automotive body modules such as seat-heater controllers, mirror-adjust switches, interior LED dimmers, and trunk-lid release timers. The industrial -40C to +85C temperature grade covers cabin and engine-bay-adjacent environments, and the HS oscillator mode tolerates the electrical noise typical of 12 V automotive buses. The 3.0-6.25 V operating range is fed directly from the vehicle's 5 V regulated rail after a TVS-protected transient filter. Note: this part is NOT AEC-Q100 qualified - for safety-critical or under-hood applications, choose PIC16F1829-I/SO or PIC16F1936-I/SO AEC-Q100 alternatives.
Recommended
Industrial Timer and Counter Modules
The PIC16C55-HSI/SO is ideal for industrial timer/counter modules where its TMR0 8-bit timer with 8-bit programmable prescaler handles pulse counting from 0 to 65536 counts at rates up to 5 MHz (1:4 ratio with CPU clock). Typical uses include conveyor-belt position encoders, flow-meter pulse accumulators, conveyor-line production counters, and packaging-machine batch counters. The 20 MHz CPU clock enables tight control loops with sub-microsecond response. Industrial -40C to +85C operation covers factory-floor environments, and the 28-SOIC SMT package supports automated pick-and-place assembly. Add a watchdog timer in software or use the optional PIC16C558-20I/SO variant if hardware WDT is needed.
Recommended
Remote Control Transmitter
The PIC16C55-HSI/SO powers simple RF remote-control transmitters for garage-door openers, ceiling-fan controllers, and toy RC vehicles. Its 33 instructions fit a complete IR (38 kHz) or RF (315/433 MHz) Manchester-encoded transmitter in under 768 B of code, including button-debounce, ID-dip-switch scanning, and transmit-repetition logic. The 20 MHz oscillator lets the firmware bit-bang carrier generation at frequencies up to 5 MHz with sub-microsecond timing accuracy. Battery life is favorable because the PIC16C5X family supports a sleep-mode current below 4 uA at 5 V, and the OTP firmware is locked once programmed.
Recommended
Glue-Logic Replacement / Discrete Logic Consolidation
The PIC16C55-HSI/SO replaces 5-15 discrete 74HC-series logic gates in products like vending-machine coin acceptors, electronic locks, and security-keypads. A typical 74HC00 + 74HC138 + 74HC595 + 74HC165 design (4 ICs, ~20 gates) consolidates into a single PIC16C55 plus 2-3 passive components, reducing PCB area by 60-70%. The 20 I/O pins and TMR0 replace counter/decoder ICs, while the OTP memory holds the lookup table for coin-pulse-width acceptance or keypad-code validation. The 200 ns instruction cycle is fast enough to emulate combinational logic with no perceptible propagation delay.
Recommended
Sensor Conditioning Front-End
The PIC16C55-HSI/SO conditions analog sensor signals in industrial monitoring systems, taking 8-bit readings from a comparator or external ADC and applying linearization, thresholding, and alarm logic before forwarding the result via GPIO to a host PLC. The 20 MHz CPU enables 10 kHz sampling loops with software-implemented sigma-delta oversampling for thermistor and RTD interfaces. Industrial -40C to +85C operation tolerates factory environments, and the OTP memory locks the calibration coefficients for each unit. The 28-SOIC SMT footprint supports compact PCB designs in DIN-rail-mounted sensor modules.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C55-HSI/SO — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C55-HSI/P | PIC16C55AT-20/SO | PIC16C55-10/SO | PIC16F54-I/SO | PIC16C558-20/SO |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | SOIC-28 (7.50 mm) | PDIP-28 (through-hole, same pinout) | SOIC-28 (same) | SOIC-28 (same) | SOIC-28 (same) | SOIC-28 (same) |
| 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) | 512 B (flash, -33%) | 768 B (512 x 12 OTP) |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Flash (in-circuit reprogrammable) | OTP EPROM |
| Max CPU Clock | 20 MHz | 20 MHz | 20 MHz | 10 MHz (-50%) | 20 MHz | 20 MHz |
| RoHS Compliance | Non-RoHS (SnPb finish) | Non-RoHS (SnPb) | Non-RoHS (SnPb) | Non-RoHS (SnPb) | RoHS compliant | Non-RoHS (SnPb) |
| Lifecycle Status | NRND | NRND | NRND | NRND | Active | NRND |
| Operating Temperature | -40C to +85C (industrial) | -40C to +85C (industrial) | -40C to +85C (industrial) | -40C to +70C (commercial) | -40C to +85C (industrial) | -40C to +70C (commercial) |
| Unit Price (qty 1) | $1.97 | $2.10 (approx) | $1.95 (approx) | $1.85 (approx) | $1.65 (approx) | $1.90 (approx) |
Key Differentiators
- Through-hole drop-in upgrade path (vs PIC16C55-HSI/P)
- Flash-based modern successor (vs PIC16F54-I/SO)
- Cost-optimized 10 MHz variant (vs PIC16C55-10/SO)
Design Notes
Estimated: At 20 MHz and 5 V supply, PIC16C55-HSI/SO draws approximately 15-20 mA active and 4 uA in sleep. Add a 100 nF ceramic decoupling capacitor within 5 mm of the VDD pin (pin 25) and a 10 uF bulk capacitor at the regulator output. The VSS pin (pin 5, plus pin 24 on SOIC) must both be connected to a solid ground plane for stable oscillator operation. The MCLR pin (pin 4) requires a 10 kohm pull-up to VDD; do not leave it floating.
The PIC16C55-HSI/SO is OTP (One-Time-Programmable) - the SOIC package has NO erasure window, so code is committed permanently at first programming. For development cycles, use the JW (windowed CERDIP) variant of the same die with a UV eraser, or migrate to PIC16F54-I/SO which is flash-based. Do not confuse the HS suffix with Hi-Speed USB - it stands for High-Speed oscillator mode (crystal/ceramic resonator up to 20 MHz).
Place the crystal or ceramic resonator within 5 mm of pins 6 (OSC1) and 7 (OSC2). Use short, symmetric traces and surround the oscillator traces with a ground pour to minimize radiated EMI. For HS mode at 20 MHz, add 15-33 pF load capacitors from each oscillator pin to ground; the exact value depends on the crystal's load capacitance specification. The 28-SOIC footprint has 1.27 mm pin pitch - ensure your PCB land pattern matches JEDEC MS-013.
Compliance Information
Non-RoHS due to SnPb lead finish on legacy 28-SOIC package. Not AEC-Q100 qualified - for automotive safety applications, choose PIC16F1936-I/SO. Reach and conflict-minerals compliance per Microchip product declaration.
