PIC17C42AT-25E/L
PIC17C42AT-25E/L - 25MHz 8-bit OTP MCU 4KB Flash 44-PLCC
The Microchip Technology PIC17C42AT-25E/L is a high-performance 8-bit CMOS EPROM/ROM microcontroller in the PIC17C family, featuring a 25 MHz core speed, 4 KB (2K x 16) of One-Time-Programmable (OTP) program memory, and 232 bytes (232 x 8) of data RAM, all housed in a 44-pin PLCC (Plastic Leaded Chip Carrier) package measuring 16.59 x 16.59 mm. The part number suffix "E" indicates the extended industrial temperature range, and "T/" denotes tape-and-reel packaging for high-volume surface-mount assembly lines.
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory, data RAM, and peripheral interfaces into one device. The PIC17C family represents Microchip's earliest high-end 8-bit architecture and occupies a position above the mainstream PIC16F mid-range devices but below the PIC18 enhanced family in the hierarchy: MCU -> 8-bit MCU -> PIC architecture -> PIC17C high-performance family. The 17C42A was the first PIC to break the 4 MHz MIPS barrier of the classic mid-range, addressing state-machine and control applications that needed higher throughput.
Key differentiating features of the PIC17C42AT-25E/L include a 16-bit-wide instruction word (vs. 14-bit in PIC16), an 8-level hardware stack, a hardware multiply unit, and 33 digital I/O pins grouped into five ports (RA, RB, RC, RD, RE). On-chip peripherals cover the era's standard control interface set: one USART (UART), one capture/compare/PWM (CCP) module, Power-On Reset (POR), Brown-Out Reset (BOR), a Watchdog Timer (WDT), and two 8-bit timers plus one 16-bit timer. The device requires an external oscillator or resonator, with crystal frequencies up to 25 MHz providing 10 MIPS sustained throughput.
Architecturally, the PIC17C42A uses a Harvard memory layout with separate program and data buses, executed through a two-stage pipeline. Its OTP EPROM cell allows one-time programming by the user or via a third-party programming house, which was the dominant in-system programmable option before Flash memory replaced EPROM. The die is implemented in CMOS technology, giving the part the typical low-power characteristics of the era, with typical active current in the 30 mA range at 25 MHz.
Typical applications include industrial motor control (stepper and DC brushed), appliance control boards (washing machines, microwave ovens, HVAC blowers), automotive body and chassis subsystems, security and alarm panels, point-of-sale terminals, and embedded control replacing discrete logic. The wide temperature range of -40 °C to +125 °C (E suffix) makes it suitable for under-hood and outdoor installations, while the 25 MIPS throughput is enough for closed-loop PID control loops at modest switching frequencies.
A key design consideration is that this part is OTP, meaning code cannot be erased and rewritten in-circuit. Engineers should prototype with the UV-erasable windowed version (PIC17C42A-25/L) and finalize firmware before committing to OTP production parts. Plan for a programming step in manufacturing rather than relying on in-system firmware updates, and budget for any last-minute code changes by keeping the windowed part in the engineering bill of materials.
This page synthesizes distributor pricing, datasheet specifications, and drop-in alternative options for engineers still maintaining or redesigning legacy PIC17C42A-based systems, including verified same-package alternatives and package-family trade-offs.
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