4-bit computing

transmission 4-bit microcontroller transmitter controlled by a NEC D63GS 4-bit microcontroller A 4-bit processor may seem limited, but it is a good match for calculators, where each decimal digit fits into four bits. It contained a 4-bit CPU with a Harvard architecture and 8-bit-wide instructions, an on-chip instruction ROM, and an on-chip data RAM with 4-bit words. The 4-bit processors were programmed in assembly language or Forth, e.g. "MARC4 Family of 4 bit Forth CPU" sometimes called "nybble-serial". The HP Saturn processors, used in many Hewlett-Packard calculators between 1984 and 2003 (including the HP 48 series of scientific calculators) are "4-bit" (or hybrid 64-/4-bit) machines. They string multiple 4-bit words together, e.g. to form a 20-bit memory address, and most of the registers are 64 bits wide, storing 16 4-bit digits. Operations were performed nybble-serial. == Uses ==

One bicycle computer specifies that it uses a "4 bit, 1-chip microcomputer". Several manufacturers used 4-bit microcontrollers in their early electronic games: • Mattel's Funtronics Jacks, Red Light Green Light, Tag, Plus One and Dalla$. • Milton Bradley Lightfight and Electronic Battleship 1982. • Coleco Head to Head Basketball. • National Semiconductor Quiz Kid Racer. • Entex Space Invader. • Texas Instruments My Little Computer. Western Digital used a 4-bit microcontroller as the basis for their WD2412 time-of-day clock. The Grundy Newbrain computer uses a 4-bit microcontroller to manage its keyboard, tape I/O, and its built-in 16 character VF alphanumeric display. The Apple Lisa utilizes a 4-bit microcontroller to control the keyboard, mouse, RTC, and soft power switch. == Details ==

With 4 bits, it is possible to create 16 different values. All single-digit hexadecimal numbers can be written with four bits. Binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by four bits. == List of 4-bit processors ==

4-bit microcontroller • Intel 4004 (first 4-bit microprocessor and widely regarded as the first commercially available microprocessor from 1971, discontinued 1981) • Intel 4040 (discontinued 1981) • TMS 1000 (the first high-volume commercial microcontroller, from 1974, after Intel 4004; now discontinued) • American Microsystems S2000 • Atmel MARC4 core • National Semiconductor MAPS MM570X • Rockwell PPS-4 • Sharp SM590/SM591/SM595 • Sharp SM550/SM551/SM552 • Sharp SM578/SM579 • Sharp SM5E4 • Sharp LU5E4POP • Sharp SM5J5/SM5J6 • Sharp SM530 • Sharp SM531 • Sharp SM500 (ROM 1197×8 bit, RAM 40×4 bit, a divider and 56-segment LCD driver circuit) • Sharp SM5K1 • Sharp SM4A • Sharp SM510 (ROM 2772×8 bit, RAM 128×4 bit, a divider and 132-segment LCD driver circuit) • Sharp SM511/SM512 (ROM 4032×8 bit, RAM 128/142×4 bit, a divider and 136/200-segment LCD driver circuit) • Sharp SM563 == See also ==