Motorola MC14500B

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1-bit microprocessor MC14500BCP

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


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.


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]


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[edit]

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.

See also[edit]


  1. ^ Gregory, Vernon "Vern" C.; Dellande, Brian; DiSilvestro, Ray; Malarkey, Terry; Smith, Phil; Hadley, Mike (1977). Motorola MC14500B Industrial Control Unit Handbook - Theory and Operation of a CMOS one-bit processor compatible with B series CMOS devices (PDF). Motorola Semiconductor Products Inc. 33-B78/8.0. Archived (PDF) from the original on 2022-02-20. Retrieved 2017-05-20. [1] (2+iii+106+1 pages) (NB. Also available in German language under the title "Motorola MC14500B Industrial Control Unit Handbuch - Theorie und Anwendung eines Ein-Bit-CMOS-Prozessors".)
  2. ^ a b c Industrial Control Unit MC14500B (PDF). Semiconductor Technical Data (revision 3 ed.). Motorola. 1995. pp. 306–313. Archived (PDF) from the original on 2017-05-20. Retrieved 2012-08-01. {{cite book}}: |work= ignored (help)
  3. ^ Cracea, Dumitru; Raiu, Dan (1990). Full Line Condensed Catalog 1990 (PDF). I.P.R.S. Băneasa. Archived (PDF) from the original on 2022-05-11. Retrieved 2022-06-17.
  4. ^ Ludwig, Volker; Paschenda, Klaus; Schepers, Heinz; Terglane, Hermann-Josef; Grannemann, Klaus; John, Burkhard; Komar, Hermann; Meinersen, Ludwig (1986). Written at Neuss & Recklinghausen, Germany. Fast alles über den WDR-1-Bit-Computer (PDF) (in German). Neuss, Germany: DATANorf. Archived (PDF) from the original on 2017-05-20. Retrieved 2017-05-20.

Further reading[edit]

External links[edit]