NEC μCOM-4
Developer	NEC
Manufacturer	NEC
Type	Microcontrollers
Production	October, 1977
Architecture	4-bit
Word size	4 bit 0.5 octets 1 nibbles
Technology	pMOS, CMOS
Clock	150 kHz-440 kHz
Package	DIP28, DIP42

The μCOM-4 (or uCOM-4) line is an extended family of 4-bit microcontrollers developed by NEC in the late 1970s. This family was designed to be low-cost, mass-produced, microcontrollers for ECRs, industrial controllers, appliance controllers, games, toys, scientific calculators, and other consumer electronics. The μCOM-4 line is based on the μPD751, the first Japanese single-chip microprocessor.

Introduction Date

1977				1980
Q1	Q2	Q3	Q4	Q1	Q2	Q3	Q4
μCOM-42	μCOM-43	μCOM-44	μCOM-45			μCOM-75

Families

The μCOM-4 was original divided into two separate domains:

μCOM-42

The μCOM-42 was specifically marketed for electronic cash registers (ECRs), Point of Sale (POS), and electronic scale applications. The μCOM-42 chips were specifically designed for controlling 8x4 keyboards, 8-digit displays, and various ECR-type printers. The μCOM-42 had a separate, modified instruction set, compared with the rest of the μCOM-4 families.

μCOM-43/44/45

The μCOM-43/44/45 was marketed as a general-purpose microcontroller suited for a large array of low-cost consumer and industrial applications. These MCUs shared a common instruction set.

• μCOM-43 - high-end family of MCUs, offering complete support for the entire μCOM-4 ISA.
• μCOM-44 - mid-range family of MCUs, providing a subset of 58 instructions at a reduced cost.
• μCOM-45 - low-end family of MCUs, providing a subset of 58 instructions and less memory at the cheapest price.

Design

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Instruction set

Main article: μCOM-4 ISA

The family was originally split into two sets of ISAs. The μCOM-42 had an instruction set specifically designed to facilitate its use in Electronic Cash Register (ECR) and Scale products. The μCOM-43/4/5 were designed to be general purpose microcontrollers.

See also

• μCOM-8

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