4-bit computing

Last updated

4-bit computing is the use of computer architectures in which integers and other data units are 4 bits wide. 4-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. A group of four bits is also called a nibble and has 24 = 16 possible values.

Contents

4-bit processors were widely used in electronic calculators and other roles where decimal math was used, like electronic cash registers, microwave oven timers, and so forth. This is because a 4-bit value holds a single binary coded decimal (BCD) digit, making it a natural size for directly processing decimal values. As a 4-bit value is generally too small to hold a memory address for real-world programs or data, the address bus of these systems was generally larger. For instance, the canonical 4-bit microprocessor, the Intel 4004, had a 12-bit address format.

4-bit designs were used only for a short period when integrated circuits were still expensive, and were found primarily in cost-sensitive roles. While 4-bit computing is mostly obsolete, 4-bit values are still used in the same decimal-centric roles they were developed for, and modern implementations are generally much wider and process multiple 4-bit values in parallel. An example of such a system is the HP Saturn design of the 1980s. By the 1990s, most such uses had been replaced by general purpose binary designs.

History

20-pin PSOP - NEC D63GS: a 4-bit microcontroller for infrared remote control transmission Alps remote control BHR970001B - NEC D63GS-7525.jpg
20-pin PSOP - NEC D63GS: a 4-bit microcontroller for infrared remote control transmission
16-pin DIP - Intel C4004 Intel C4004 greytraces CPU.jpg
16-pin DIP - Intel C4004
Olympia CD700 Desktop Calculator using the National Semiconductor MAPS MM570X bit-serial 4-bit microcontroller Olympia CD700 Desktop Calculator. 1971.Microprogrammable Arithmetic Processor System Devices (MAPS).jpg
Olympia CD700 Desktop Calculator using the National Semiconductor MAPS MM570X bit-serial 4-bit microcontroller
Infrared remote control PCB - an infrared remote control transmitter controlled by a NEC D63GS 4-bit microcontroller Alps remote control BHR970001B-7517.jpg
Infrared remote control PCB - an infrared remote control 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. [1]

Some of the first microprocessors had a 4-bit word length and were developed around 1970. The first commercial microprocessor was the binary-coded decimal (BCD-based) Intel 4004, [2] [3] developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses. It was succeeded by the Intel 4040, which added interrupt support and a variety of other new features.

The first commercial single-chip computer was the 4-bit Texas Instruments TMS 1000 (1974). [1] 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. [4]

The Rockwell PPS-4 was another early 4-bit processor, introduced in 1972, which had a long lifetime in handheld games and similar roles. It was steadily improved and by 1975 been combined with several support chips to make a one-chip computer. [5]

The 4-bit processors were programmed in assembly language or Forth, e.g. "MARC4 Family of 4 bit Forth CPU" [6] (which is now discontinued) because of the extreme size constraint on programs and because common programming languages (for microcontrollers, 8-bit and larger), such as the C programming language, do not support 4-bit data types (C, and C++, and more languages require that the size of the char data type be at least 8 bits, [7] and that all data types other than bitfields have a size that is a multiple of the character size [8] [9] [10] ).

The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators. During the 1980s, 4-bit microprocessors were used in handheld electronic games to keep costs low.

In the 1970s and 1980s, a number of research and commercial computers used bit slicing, in which the CPU's arithmetic logic unit (ALU) was built from multiple 4-bit-wide sections, each section including a chip such as an Am2901 or 74181.

The Zilog Z80, although it is an 8-bit microprocessor, has a 4-bit ALU. [11] [12]

Although the Data General Nova is a series of 16-bit minicomputers, the original Nova and the Nova 1200 internally processed numbers 4 bits at a time with a 4-bit ALU, [13] sometimes called "nybble-serial". [14]

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; as the Intel 4004 did, 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. [15] [16] [17]

In addition, some early calculators – such as the 1967 Casio AL-1000, the 1972 Sinclair Executive, and the aforementioned 1984 HP Saturn  – had 4-bit datapaths that accessed their registers 4 bits (one BCD digit) at a time. [18]

Uses

One bicycle computer specifies that it uses a "4 bit, 1-chip microcomputer". [19] Other typical uses include coffee makers, infrared remote controls, [20] and security alarms. [21]

The processor in Barbie typewriters that can encrypt is a 4-bit microcontroller. [22]

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

National Semiconductor MM5700CA/D bit-serial 4-bit microcontroller National Semiconductor MM5700CA D Microprocessor.jpg
National Semiconductor MM5700CA/D bit-serial 4-bit microcontroller

See also

Related Research Articles

<span class="mw-page-title-main">Microprocessor</span> Computer processor contained on an integrated-circuit chip

A microprocessor is a computer processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, and control circuitry required to perform the functions of a computer's central processing unit (CPU). The IC is capable of interpreting and executing program instructions and performing arithmetic operations. The microprocessor is a multipurpose, clock-driven, register-based, digital integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. Microprocessors contain both combinational logic and sequential digital logic, and operate on numbers and symbols represented in the binary number system.

<span class="mw-page-title-main">Microcontroller</span> Small computer on a single integrated circuit

A microcontroller or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs along with memory and programmable input/output peripherals. Program memory in the form of ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips.

In computer architecture, 8-bit integers or other data units are those that are 8 bits wide. Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. Memory addresses for 8-bit CPUs are generally larger than 8-bit, usually 16-bit. 8-bit microcomputers are microcomputers that use 8-bit microprocessors.

<span class="mw-page-title-main">MCS-51</span> Single chip microcontroller series by Intel

The Intel MCS-51 is a single chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems. The architect of the Intel MCS-51 instruction set was John H. Wharton. Intel's original versions were popular in the 1980s and early 1990s, and enhanced binary compatible derivatives remain popular today. It is a complex instruction set computer, but also has some of the features of RISC architectures, such as a large register set and register windows, and has separate memory spaces for program instructions and data.

<span class="mw-page-title-main">Zilog</span> American manufacturer of microprocessors

Zilog, Inc. is an American manufacturer of microprocessors and 8-bit and 16-bit microcontrollers. It is also a supplier of application-specific embedded system-on-chip (SoC) products.

<span class="mw-page-title-main">Intel 8008</span> 8-bit microprocessor

The Intel 8008 is an early byte-oriented microprocessor designed by Computer Terminal Corporation (CTC), implemented and manufactured by Intel, and introduced in April 1972. It is an 8-bit CPU with an external 14-bit address bus that could address 16 KB of memory. Originally known as the 1201, the chip was commissioned by CTC to implement an instruction set of their design for their Datapoint 2200 programmable terminal. As the chip was delayed and did not meet CTC's performance goals, the 2200 ended up using CTC's own TTL-based CPU instead. An agreement permitted Intel to market the chip to other customers after Seiko expressed an interest in using it for a calculator.

<span class="mw-page-title-main">Intel 4004</span> 4-bit microprocessor

The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. Sold for US$60, it was the first commercially produced microprocessor, and the first in a long line of Intel CPUs.

<span class="mw-page-title-main">Intel 4040</span> 4-bit microprocessor introduced in 1974 by Intel

The Intel 4040 microprocessor was the successor to the Intel 4004, introduced in 1974. The 4040 employed a 10 μm silicon gate enhancement-load PMOS technology, was made up of 3,000 transistors and could execute approximately 62,000 instructions per second.

<span class="mw-page-title-main">Masatoshi Shima</span> Japanese electronics engineer

Masatoshi Shima is a Japanese electronics engineer. He was one of the architects of the world's first microprocessor, the Intel 4004. In 1968, Shima worked for Busicom in Japan, and did the logic design for a specialized CPU to be translated into three-chip custom chips. In 1969, he worked with Intel's Ted Hoff and Stanley Mazor to reduce the three-chip Busicom proposal into a one-chip architecture. In 1970, that architecture was transformed into a silicon chip, the Intel 4004, by Federico Faggin, with Shima's assistance in logic design.

<span class="mw-page-title-main">Busicom</span> Japanese company

Busicom Co., Ltd. was a Japanese company that manufactured and sold computer-related products headquartered in Taito, Tokyo. It owned the rights to Intel's first microprocessor, the Intel 4004, which they created in partnership with Intel in 1970.

Bit slicing is a technique for constructing a processor from modules of processors of smaller bit width, for the purpose of increasing the word length; in theory to make an arbitrary n-bit central processing unit (CPU). Each of these component modules processes one bit field or "slice" of an operand. The grouped processing components would then have the capability to process the chosen full word-length of a given software design.

<span class="mw-page-title-main">History of general-purpose CPUs</span> History of processors used in general purpose computers

The history of general-purpose CPUs is a continuation of the earlier history of computing hardware.

Each time Intel launched a new microprocessor, they simultaneously provided a system development kit (SDK) allowing engineers, university students, and others to familiarise themselves with the new processor's concepts and features. The SDK single-board computers allowed the user to enter object code from a keyboard or upload it through a communication port, and then test run the code. The SDK boards provided a system monitor ROM to operate the keyboard and other interfaces. Kits varied in their specific features but generally offered optional memory and interface configurations, a serial terminal link, audio cassette storage, and EPROM program memory. Intel's Intellec development system could download code to the SDK boards.

In computer architecture, 16-bit integers, memory addresses, or other data units are those that are 16 bits wide. Also, 16-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 16-bit microcomputers are microcomputers that use 16-bit microprocessors.

<span class="mw-page-title-main">Texas Instruments TMS1000</span>

The TMS1000 is a family of microcontrollers introduced by Texas Instruments in 1974.

<span class="mw-page-title-main">78K</span> Microcontroller family

78K is the trademark name of 16- and 8-bit microcontroller family manufactured by Renesas Electronics, originally developed by NEC started in 1986. The basis of 78K Family is an accumulator-based register-bank CISC architecture. 78K is a single-chip microcontroller, which usually integrates; program ROM, data RAM, serial interfaces, timers, I/O ports, an A/D converter, an interrupt controller, and a CPU core, on one die.

The NEC μCOM series is a series of microprocessors and microcontrollers manufactured by NEC in the 1970s and 1980s. The initial entries in the series were custom-designed 4 and 16-bit designs, but later models in the series were mostly based on the Intel 8080 and Zilog Z80 8-bit designs, and later, the Intel 8086 16-bit design. Most of the line was replaced in 1984 by the NEC V20, an Intel 8088 clone.

<span class="mw-page-title-main">COP400</span> 4-bit microcontroller family

The COP400 or COP II is a 4-bit microcontroller family introduced in 1977 by National Semiconductor as a follow-on product to their original PMOS COP microcontroller. COP400 family members are complete microcomputers containing internal timing, logic, ROM, RAM, and I/O necessary to implement dedicated controllers. Some COP400 devices were second-sourced by Western Digital as the WD4200 family. In the Soviet Union several COP400 microcontrollers were manufactured as the 1820 series.

<span class="mw-page-title-main">Rockwell PPS-4</span> 4-bit microprocessor

The Rockwell PPS-4, short for "Parallel Processing System, 4-bit", was an early 4-bit microprocessor from Rockwell International, released in late 1972. Although practically unknown today, the PPS series was widely used in calculators, games and toys, and other embedded applications. Updated versions continued to be produced into the 1980s.

References

  1. 1 2 Ken Shirriff. "Reverse engineering RAM storage in early Texas Instruments calculator chips".
  2. ↑ Mack, Pamela E. (2005-11-30). "The Microcomputer Revolution" . Retrieved 2009-12-23.
  3. ↑ "History in the Computing Curriculum" (PDF). Archived from the original (PDF) on 2011-07-19. Retrieved 2017-06-22.
  4. ↑ TMS 1000 Series Data Manual (PDF). Texas Instruments. December 1976. Retrieved 2013-07-20.
  5. ↑ "Rockwell PPS-4".
  6. ↑ "Forth Chips". www.ultratechnology.com.
  7. ↑ ISO/IEC 9899:1999 specification. p. 20, § 5.2.4.2.1. Retrieved 2023-07-24.
  8. ↑ ISO/IEC 9899:1999 specification. p. 37, § 6.2.6.1 (4). Retrieved 2023-07-24.
  9. ↑ Cline, Marshall. "C++ FAQ: the rules about bytes, chars, and characters".
  10. ↑ "4-bit integer". cplusplus.com. Retrieved 2014-11-21.
  11. ↑ Shima, Masatoshi; Faggin, Federico; Ungermann, Ralph; Slater, Michael (2007-04-27). "Zilog Oral History Panel on the Founding of the Company and the Development of the Z80 Microprocessor" (PDF).
  12. ↑ Shirriff, Ken. "The Z-80 has a 4-bit ALU".
  13. ↑ Hendrie, Gardner (2002-11-22). "Oral History of Edson (Ed) D. de Castro" (PDF) (Interview). p. 44.
  14. ↑ "Nova 1200"
  15. ↑ "The Saturn Processor" . Retrieved 2015-12-23.
  16. ↑ "Guide to the Saturn Processor" . Retrieved 2014-01-14.
  17. ↑ "Introduction to Saturn Assembly Language" . Retrieved 2014-01-14.
  18. ↑ "Desk Electronic Calculators: Casio AL-1000"
  19. ↑ "Cateye Commuter Manual" (PDF). Retrieved 2014-02-11.
  20. 1 2 "μPD67, 67A, 68, 68A, 69 4-bit single-chip microcontroller for infrared remote control transmission" (PDF). documentation.renesas.com. Archived from the original (PDF) on 2016-01-06.
  21. ↑ Haskell, Richard. "Introduction to Digital Logic and Microprocessors (Lecture 12.2)". Archived from the original on 2014-02-22. Retrieved 2014-02-11.
  22. ↑ Paul Reuvers and Marc Simons. Crypto Museum. "Barbie Typewriter", 2015
  23. ↑ "MARC4 4-bit Microcontrollers – Programmer's Guide" (PDF). Atmel. Archived from the original (PDF) on 2014-12-15. Retrieved 2014-01-14.
  24. ↑ "MARC4 4-Bit Architecture". Atmel. Archived from the original on 2009-05-31.
  25. ↑ "Product End-of-Life (EOL) Notification" (PDF). Atmel. 2014-03-07. Archived from the original (PDF) on 2016-08-07.
  26. ↑ "μPD6P9 4-bit single-chip microcontroller for infrared remote control transmission" (PDF). documentation.renesas.com. Archived from the original (PDF) on 2016-03-27.
  27. ↑ "μPD17240, 17241, 17242, 17243, 17244, 17245, 17246 4-bit single-chip microcontrollers for small general-purpose infrared remote control transmitters" (PDF). documentation.renesas.com. Archived from the original (PDF) on 2016-03-27.
  28. ↑ "Microcontrollers for Remote Controllers" (PDF). documentation.renesas.com. Archived from the original (PDF) on 2013-12-19.
  29. ↑ "Mask ROM/ROMless Products 4/8bit Remote Control". Archived from the original on 2008-10-28.
  30. ↑ Cravotta, Robert. "Embedded Processing Directory".
  31. ↑ "EM6580". Archived from the original on 2013-12-19. Retrieved 2013-05-12.
  32. ↑ "EM6580".
  33. ↑ "EM6682".
  34. ↑ Culver, John (2014-09-27). "National Semiconductor: The COP before the COPS". www.cpushack.com. Retrieved 2020-05-28.
  35. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Sharp Microcomputers Data Book (PDF). September 1990. Retrieved 2018-01-05.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.