20 MHz 8-bit core with OTP firmware lock
The PIC16C66-20I/SO is an 8-bit PIC MCU from Microchip's PIC® 16C family, clocked at 20 MHz. It packs 14 KB (8K x 14) of OTP program memory — once programmed, the firmware is permanent. That makes it a fit for high-volume, locked-code production where field updates are not part of the plan.
The 4V to 6V supply range means it runs directly off a 5V rail or an unregulated battery — no extra regulator, no 3.3V translation.
Peripherals and I/O — what connects where
22 I/O lines give enough headroom for a keypad, a few sensors, and a small display. On-chip peripherals include a PWM for motor or LED dimming, a watchdog timer, and brown-out detect/reset for reliable power-up sequencing.
Package and rework — 28-SOIC, 7.50 mm body
Housed in a 28-SOIC (0.295-inch, 7.50 mm width) — a gull-wing leaded package that reworks cleanly under hot air.