The MC14500B Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977.^[1]

Overview

MC14500B (ICU) is well-suited to the implementation of ladder logic, and thus could be used to replace relay systems and programmable logic controllers, also intended for serial data manipulation.^[2] The processor supports 16 commands, operating at a frequency of 1 MHz.^[2] The MC14500B unit does not include a program counter (PC); instead, a clock signal drives a separate PC chip; therefore the size of supported memory is dependent on the implementation of that chip. It was still in production in 1995.^[2]

The ICU architecture is similar to that of the DEC PDP-14 computer.

Developers

The ICU was conceived by Vern Gregory in the mid-1970s while working as an engineer in a marketing / applications group of Motorola Semiconductor Products Sector in Phoenix, Arizona, USA; Brian Dellande originated circuit and sub-routine designs, and co-wrote the manual; Ray DiSilvestro was the bench technician; Terry Malarkey provided management support.^{[citation needed]}

In the CMOS Logic Division in Austin, Texas, USA (where it was made) Phil Smith was the chip designer; Mike Hadley provided product applications support.^{[citation needed]}

Derivatives

A form of the design served as an embedded controller in a custom automotive chip made for Nippon Denso by Motorola—Japan.

I.P.R.S. Băneasa manufactured a clone of the MC14500B with the designation βP14500 in IIL technology (rather than the original CMOS).^[3]

Notable uses

One of the computers known to be based on this processor is the educational WDR 1-bit computer (512 bits of RAM, LED, I/O, keyboard).^[4]

A modern take, in retro style, of a computer based on this processor is the PLC14500-Nano. It is certified as Open Source Hardware PL000011 so anyone can learn from its design and can freely build it.