Motorola MC14500
1-bit microprocessor for industrial controls
The MC14500 Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977. It was packaged in a 16-pin DIP and normally ran at 1 MHz with 5 V and only 5 μA. If higher performance was needed, it could run as fast as 4 MHz by increasing the voltage to 15 V. It was inexpensive for the era, available at launch for $7.58 in 100-unit lots.
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. The processor supports 16 commands, operating at a frequency of 1 MHz. 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.
The ICU architecture is similar to that of the DEC PDP-14 computer.
The MC14500B was implemented with a transistor count of roughly 500 transistors. The chip was so simple not only because it only handled 1-bit computing data at a time, but also because the chip did not include a program counter, subroutine stack, etc. -- those required external chips.
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This entry incorporates text from “Motorola MC14500” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.