Motorola MC14500
The MC14500 Industrial Control Unit (ICU) is a CMOS one‑bit microprocessor built by Motorola in 1977 for simple control tasks. It comes in a 16‑pin DIP and normally runs at 1 MHz from a 5 V supply, drawing about 5 µA. If more speed is needed, it can run up to 4 MHz by increasing the voltage to 15 V. At launch, it was very affordable, listed around $7.58 for 100 units.
The MC14500B version is designed for ladder logic and can replace relays and traditional programmable logic controllers (PLCs). It can also handle serial data manipulation. It supports 16 instructions and runs at 1 MHz. Unlike most microprocessors, the MC14500B does not include a built‑in program counter; a separate PC chip provides the counter, so how much memory you can use depends on that external chip.
This ICU stayed in production through the mid‑1990s. Its architecture is very simple: it processes 1‑bit data and leaves features like a program counter or subroutine stack to external chips. The design uses about 500 transistors.
The ICU was conceived in the mid‑1970s in Motorola’s Phoenix area, with engineers contributing to its circuit designs and documentation. A version of the design was used as an embedded controller in a Nippon Denso automotive chip. Clones appeared, such as the βP14500 built in a different technology by IP.R.S. Băneasa.
The MC14500 has appeared in hobbyist and educational projects, including a 1‑bit computer based on this processor and retro designs like the PLC14500‑Nano, an Open Source Hardware project for learning and building.
This page was last edited on 3 February 2026, at 17:50 (CET).