PIC16C56AT-04/SS - 8-Bit 4MHz OTP MCU, 1.5KB | Microchip
MPN: PIC16C56AT-04/SS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.13 | $1.13 |
| 10 | $1.1 | $11.00 |
| 100 | $1 | $100.00 |
| 500 | $0.92 | $460.00 |
| 1,000 | $0.8567 | $856.70 |
PIC16C56AT-04/SS Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, data RAM, and programmable I/O peripherals. 8-bit MCUs such as the PIC16C5X occupy the low-cost, low-power segment of the embedded market, making them well-suited for appliance control, sensor signal conditioning, and standalone industrial timers where 16- or 32-bit processing is unnecessary. The PIC family uses a Harvard RISC architecture with 12-bit-wide instructions and only 33 single-word instructions, achieving 2:1 code compression over competing 8-bit architectures.
Key features of the PIC16C56AT-04/SS include 25 bytes of RAM, 12 digital I/O pins, an internal oscillator option, a Watchdog Timer with its own on-chip RC oscillator, and power-saving SLEEP mode. The device operates from 3.0V to 5.5V across the commercial 0C to +70C temperature range, drawing only a few mA active and microamp-level current in SLEEP. The fully static CMOS design allows the clock to be stopped without losing register contents, simplifying low‑power sequencing.
The PIC16C5X architecture is a classic RISC implementation with a two-stage pipeline, allowing most instructions to execute in a single 250ns instruction cycle at 4MHz. The 12-bit instruction word keeps program memory density high, and the 8-bit-wide data path is sufficient for byte-oriented control loops. Peripherals are limited intentionally to keep die size and cost low: timer/counter, GPIO, and reset logic are the primary on-chip resources. OTP program memory allows the customer to write the device once at production time, ideal for mature, fixed-function products.
Typical applications for the PIC16C56AT-04/SS include simple motor and solenoid drivers, low-end consumer appliance control (coffee makers, handhelds, toys), LED sequencing modules, automotive interior accessories, and small sensor-interface boards. The 12 I/O pins are adequate for keypad scanning, relay driving, and UART-style bit-banged communication. Because OTP is one-time programmable, this part is best suited for high-volume production where firmware is finalized before mask programming.
When designing with this device, plan for an in-circuit serial programming (ICSP) header even on production boards so OTP can be written after PCB assembly. Decouple VDD with a 100nF ceramic capacitor placed within 5mm of the pin, and provide a clean MCLR reset path with the recommended 10k pull-up. If in-application reprogrammability is required, consider a flash-based PIC16F5X equivalent.
This page synthesizes distributor pricing, drop-in same-package alternatives from the PIC16C5X family, and practical design notes that complement the manufacturer datasheet.
Drop-in alternatives for PIC16C56AT-04/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 PIC16C56AT-04/SS (same form factor and footprint) — differing in Package, Program Memory Size, Program Memory Type, Timers, Mounting Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PIC16C56A-04I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C56A-04E/SS
✅ Drop-In✓ In Stock
$1.32 / Unit
View Datasheet →PIC16C56A-20I/SS
✅ Drop-In✓ In Stock
$0.67 / Unit
View Datasheet →PIC16C56A-20E/P
✅ Drop-In✓ In Stock
$2.85 / Unit
View Datasheet →PIC16C55AT-04/SS
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →PIC16F54-I/SS
✅ Drop-In📋 Reference alternative (not in catalog)
PIC16C56AT-04/SS Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC 8-bit RISC (Harvard) |
| Program Memory Type | OTP (One-Time-Programmable) EPROM |
| Program Memory Size | 1.5 KB (1K x 12) |
| RAM Size | 25 bytes |
| Maximum CPU Frequency | 4 MHz |
| Instruction Cycle Time | 1 us at 4 MHz (4 oscillator clocks per instruction cycle) |
| Number of I/O Pins | 12 |
| Instruction Set Size | 33 single-word instructions |
| Operating Voltage Range | 3.0 V to 5.5 V |
| Operating Temperature Range | 0 C to +70 C (Commercial) |
| Package | 20-pin SSOP (5.30 mm body width) |
| Mounting Type | Surface Mount |
| On-chip Peripherals | Watchdog Timer with dedicated RC oscillator, 8-bit Timer/Counter, SLEEP mode |
| Oscillator Modes | External RC, External Crystal, External Clock |
| RoHS Status | Compliant (per TrustCompo listing) |
| Lead-Free / Halogen-Free | Lead-free per TrustCompo listing |
PIC16C56AT-04/SS Pin Configuration
| Pin 1 | RA2 — Bidirectional I/O pin, Port A bit 2 |
| Pin 2 | RA3 — Bidirectional I/O pin, Port A bit 3 (also GP input on some PIC16C5X) |
| Pin 3 | RTCC — RTCC timer/counter input pin |
| Pin 4 | MCLR — Master Clear (reset) input, active low |
| Pin 5 | VSS — Ground reference |
| Pin 6 | RB0 — Bidirectional I/O pin, Port B bit 0 |
| Pin 7 | RB1 — Bidirectional I/O pin, Port B bit 1 |
| Pin 8 | RB2 — Bidirectional I/O pin, Port B bit 2 |
| Pin 9 | RB3 — Bidirectional I/O pin, Port B bit 3 |
| Pin 10 | RB4 — Bidirectional I/O pin, Port B bit 4 |
| Pin 11 | RB5 — Bidirectional I/O pin, Port B bit 5 |
| Pin 12 | RB6 — Bidirectional I/O pin, Port B bit 6 |
| Pin 13 | RB7 — Bidirectional I/O pin, Port B bit 7 |
| Pin 14 | VDD — Positive supply voltage (3.0 V to 5.5 V) |
| Pin 15 | OSC2 — Oscillator output (crystal/RC mode) or CLKOUT |
| Pin 16 | OSC1 — Oscillator input (crystal/RC/external clock) |
| Pin 17 | RA0 — Bidirectional I/O pin, Port A bit 0 |
| Pin 18 | RA1 — Bidirectional I/O pin, Port A bit 1 |
| Pin 19 | NC — Not connected on PIC16C56A SSOP-20 variant |
| Pin 20 | NC — Not connected on PIC16C56A SSOP-20 variant |
Typical Applications
PIC16C56AT-04/SS is suitable for 6 applications: Low-Cost Consumer Appliance Control, Automotive Interior Accessory Modules, Sensor Interface and Signal Conditioning Boards, LED Sequencing and Lighting Modules, Standalone Industrial Timers and Counters, Educational and Hobbyist Embedded Projects.
Low-Cost Consumer Appliance Control
The PIC16C56AT-04/SS suits appliance control boards where 12 I/O pins, 4 MHz CPU speed, and 1.5 KB OTP memory are sufficient to handle key switch scanning, LED indicators, and relay timing logic. The 33-instruction RISC core lets a developer implement a complete state machine in well under 1 KB, leaving room for timing counters and lookup tables. The 3.0 V to 5.5 V operating range allows the MCU to share a 5 V rail with the appliance relay drivers while drawing only a few mA active, and the commercial 0 C to +70 C grade covers indoor kitchen and laundry environments. Compared with newer ARM Cortex parts, this PIC achieves the lowest possible BOM cost for fixed-function firmware.
Recommended
Automotive Interior Accessory Modules
The PIC16C56AT-04/SS is commonly used in automotive interior modules such as LED ambient lighting controllers, simple body-control submodules, and aftermarket accessory timers. Its 4 MHz CPU clock and 12 I/O pins are sufficient for PWM-based LED dimming via bit-banged output compare or a transistor driver, and the 25-byte RAM can store dimming profiles and switch debounce state. Designers typically pair it with external high-side switches, with the MCU providing logic-level control. The fully static CMOS core tolerates automotive temperature swings within the commercial grade; for under-hood use, the industrial-temperature PIC16C56A-04I/SS is recommended.
Recommended
Sensor Interface and Signal Conditioning Boards
For low-bandwidth sensor signal conditioning boards (thermistor readout, simple level detection, contact-debounce buffers), the PIC16C56AT-04/SS provides a digital-output interface that converts analog sensor inputs into clean GPIO signals for downstream controllers. Its 8-bit timer/counter can be used for time-proportional output, while SLEEP mode enables battery-friendly periodic wake-and-sample operation. With only 25 bytes of RAM, the MCU is best deployed where the host processor already handles the bulk of the algorithm and the PIC serves as a low-cost local digitizer. The 1 microsecond instruction cycle at 4 MHz is fast enough for sample rates up to a few kHz.
Recommended
LED Sequencing and Lighting Modules
The PIC16C56AT-04/SS is well matched to multi-channel LED chaser and decorative lighting modules where deterministic timing and 12 GPIO outputs are sufficient. Each output can drive an LED directly via a current-limit resistor, or sink a logic-level MOSFET for higher-current strips. The 1 microsecond instruction cycle allows PWM-style dimming in firmware without external driver ICs, and the Watchdog Timer keeps the module recovering gracefully from ESD-induced lockups in outdoor installations. Compared with using a microcontroller plus a dedicated LED driver, this single-chip approach minimizes cost for fixed light-pattern products.
Recommended
Standalone Industrial Timers and Counters
In standalone industrial timer/counter applications (machine cycle timers, event counters, conveyor pacing), the PIC16C56AT-04/SS delivers dedicated control without operator-interface overhead. The on-chip 8-bit timer/counter, combined with the Watchdog Timer, supports accurate timing of seconds-to-minutes intervals when paired with a 32.768 kHz external crystal. The 12 I/O pins are typically mapped to a 7-segment display driver, a start/stop button pair, and a relay output, all within the 1.5 KB OTP budget. The 3.0 V to 5.5 V supply range allows operation from a 24 V industrial bus through a small LDO.
Recommended
Educational and Hobbyist Embedded Projects
The PIC16C56AT-04/SS is a popular teaching platform for embedded systems courses and DIY electronics kits because of its simple 33-instruction RISC architecture, abundant documentation, and low-cost SSOP-20 breakout boards. Learners can experiment with GPIO, timers, and Watchdog Timer concepts without the complexity of modern peripherals, and the OTP EPROM programming model teaches the discipline of finalized firmware. The 4 MHz clock and 1 microsecond instruction cycle are slow enough to follow execution with a logic analyzer or scope, which is ideal for understanding pipeline behavior. Kits typically include the PIC plus a 20-pin SSOP-to-DIP adapter for breadboarding.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C56AT-04/SS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C56A-04I/SS | PIC16C56A-04E/SS | PIC16C56A-20I/SS | PIC16C56A-20E/P | PIC16C55AT-04/SS | PIC16F54-I/SS |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 20-SSOP | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same | 20-SSOP - same |
| Program Memory | 1.5 KB OTP | 1.5 KB OTP | 1.5 KB OTP | 1.5 KB OTP | 1.5 KB OTP | 768 B OTP | 512 B Flash |
| Max CPU Frequency | 4 MHz | 4 MHz | 4 MHz | 20 MHz | 20 MHz | 4 MHz | 20 MHz |
| RAM | 25 bytes | 25 bytes | 25 bytes | 25 bytes | 25 bytes | 25 bytes | 25 bytes |
| I/O Pins | 12 | 12 | 12 | 12 | 12 | 12 | 12 |
| Memory Type | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | OTP EPROM | Flash |
| Operating Temperature | 0C to +70C (Commercial) | -40C to +85C (Industrial) | -40C to +125C (Extended) | -40C to +85C (Industrial) | -40C to +125C (Extended) | 0C to +70C (Commercial) | -40C to +85C (Industrial) |
| Operating Voltage | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 2.0 V to 5.5 V |
| Re-programmable | No (OTP) | No (OTP) | No (OTP) | No (OTP) | No (OTP) | No (OTP) | Yes (Flash) |
Key Differentiators
- Commercial temperature grade for indoor appliance use (vs PIC16C56A-04I/SS)
- Lower unit cost than the flash PIC16F54-I/SS (vs PIC16F54-I/SS)
- Larger 1.5 KB OTP vs smaller PIC16C55A sibling (vs PIC16C55AT-04/SS)
Design Notes
Place a 100 nF ceramic decoupling capacitor as close as possible to the VDD pin (pin 14), with the ground return tied directly to the VSS pin (pin 5) via a short trace. For battery-powered designs, place a 10 uF bulk capacitor on the VDD rail to handle transient loads when the MCU exits SLEEP mode. The PIC16C56AT-04/SS draws only a few mA active but requires stable VDD during the MCLR rise time to guarantee a clean Power-on Reset.
OTP program memory cannot be erased or rewritten; once a device is programmed, firmware bugs require a new part. Always prototype with a windowed PIC16C5X JW device or the flash-based PIC16F54-I/SS to validate firmware before committing to OTP volume programming. Also note that the MCLR pin must NOT be left floating; tie it to VDD through a 10 kohm pull-up resistor to avoid spurious resets from ESD or capacitive coupling.
The 20-pin SSOP footprint has a 0.65 mm pin pitch, which is manageable with hand soldering but requires a fine-pitch soldering iron for rework. Keep the OSC1/OSC2 traces short and surrounded by a ground guard ring if the board is in a noisy environment, since long crystal traces pick up EMI that can shift the effective clock frequency. For SSOP land pattern design, follow the IPC-7351 nominal SSOP-20 footprint, which typically uses 0.40 mm wide pads with 0.30 mm solder mask expansion.
Route the Watchdog Timer enable fuse separately from the oscillator configuration, and keep the CONFIG word visible in source control so that any board spin records the exact fuse settings. In SSOP-20 layouts, the EP (exposed pad) is absent, so thermal dissipation relies on the 20 standard leads; ensure at least 100 mil of 1 oz copper connected to VSS on each side for modest self-heating relief when the MCU is running near full I/O load.
The PIC16C56AT-04/SS has no integrated Schmitt trigger on all inputs; long PCB traces on RA/RB pins can cause double-triggering in noisy environments. Add an external RC filter (10 kohm + 100 pF) on switch inputs to suppress contact bounce and EMI. For RTCC pin usage as a counter input, keep traces under 25 mm and avoid routing near switching power lines that could couple into the TMR0 counter.
Compliance Information
RoHS and lead-free status confirmed by TrustCompo listing (https://trustcompo.com/product/detail/TCE000047005-PIC16C56AT-04-SS). REACH, halogen-free, and conflict minerals declarations not explicitly listed by the distributors in the verified web data; consult Microchip's product compliance page for definitive statements.