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The MCS-48 microcontroller (µC) series, Intel's first microcontroller, was originally released in 1976. Its first members were 8048, 8035 and 8748. Initially this family was produced using NMOS-technology, in the early 1980s it became available in CMOS-technology. It was still manufactured into the 1990s to support older designs that still used it.

The MCS-48 series has a Modified Harvard architecture, with internal or external program ROM and 64–256 bytes of internal (on-chip) RAM. The I/O is mapped into its own address space, separate from programs and data. The 8048 is probably the most prominent member of Intel's MCS-48 family of microcontrollers. It was inspired by, and is somewhat similar to, the Fairchild F8 microprocessor.

Though the MCS-48 series was eventually replaced by the very popular Intel MCS-51, even at the turn of the millennium it remains quite popular, due to its low cost, wide availability, memory efficient one-byte instruction set, and mature development tools. Because of this it is much used in high-volume consumer electronics devices such as TV sets, TV remotes, toys, and other gadgets where cost-cutting is essential.


The 8049 has 2 KB of masked ROM (the 8748 and 8749 had EPROM) that can be replaced with a 4 KB external ROM, as well as 128 bytes of RAM and 27 I/O ports. The µC's oscillator block divides the incoming clock into 15 internal phases, thus with its 11 MHz max. crystal one gets 0.73 MIPS (of one-clock instructions). Some 70% of instructions are single byte/cycle ones, but 30% need two cycles and/or two bytes, so the raw performance would be closer to 0.5 MIPS.

Philips Semiconductors (now NXP) owned a license to produce this series and developed their MAB8400-family based on this architecture. These were the first microcontrollers with an integrated I²C-interface and were used in the first Philips (Magnavox in the US) Compact Disc players (e.g. the CD-100).[1]

Another variant, the ROM-less 8035, was used in Nintendo's arcade game Donkey Kong. Although not being a typical application for a microcontroller, its purpose was to generate the background music of the game.

The Intel 8748 has on-chip clock oscillator, 2 8-bit timers, 27 I/O ports, 64 bytes of RAM and 1 KB of EPROM. A version with 2 KB EPROM and 128 bytes RAM was also available under the 8749 number.

Device  Internal          Memory        Remarks
8020    1K × 8 ROM         64 × 8 RAM   Subset of 8048, 20 pins, Only 13 I/O Lines
8021    1K × 8 ROM         64 × 8 RAM   Subset of 8048, 28 pins, 21 I/O Lines
8022    2K × 8 ROM         64 × 8 RAM   Subset of 8048, A/D-converter
8035    none               64 × 8 RAM
8039    none              128 × 8 RAM
8040    none              256 × 8 RAM
8048    1K × 8 ROM         64 × 8 RAM
8049    2K × 8 ROM        128 × 8 RAM
8050    4K × 8 ROM        256 × 8 RAM
8748    1K × 8 EPROM       64 × 8 RAM
8749    2K × 8 EPROM      128 × 8 RAM
8648    1K × 8 OTP EPROM   64 × 8 RAM   Factory OTP EPROM
Device  Internal          Memory        Remarks
8041    1K × 8 ROM         64 × 8 RAM   Universal Peripheral Interface (UPI)
8041AH  1K × 8 ROM        128 × 8 RAM   UPI
8741A   1K × 8 EPROM       64 × 8 RAM   UPI, EPROM version of 8041
8741AH  1K × 8 OTP EPROM  128 × 8 RAM   UPI, OTP EPROM version of 8041AH
8042AH  2K × 8 ROM        256 × 8 RAM   UPI
8742    2K × 8 EPROM      128 × 8 RAM   UPI, EPROM version
8742AH  2K × 8 OTP EPROM  256 × 8 RAM   UPI, OTP EPROM version of 8042AH


The 8048 was used in the Magnavox Odyssey² video game console, the Korg Trident series , the Korg Poly-61,[2] Roland Jupiter-4 and Roland ProMars[3] analog synthesizers.

The original IBM PC keyboard used an 8048 as its internal microcontroller.[4] The PC AT replaced the PC's Intel 8255 peripheral interface chip at I/O port addresses 0x60-63 with an 8042 accessible through port addresses 0x60 and 0x64.[5] As well as managing the keyboard interface the 8042 controlled the A20 line of the AT's Intel 80286 CPU, and could be commanded by software to reset the 80286 (unlike the 80386 and later processors, the 80286 had no way of switching from protected mode back to real mode except by being reset). Later PC compatibles integrate the 8042's functions into their super I/O devices.


  • MCS-48 Single Component Microcomputer, Applications Seminar Notebook, 1978, Intel Corporation.
  • , 1978, Intel Corporation.
  • Lionel Smith, Cecil Moore: Serial I/O and Math Utilities for the 8049 Microcomputer, Application Note AP-49, January 1979, Intel Corporation.
  • A High-Speed Emulator for Intel MCS-48 Microcomputers, Application Note AP-55A, August 1979, Intel Corporation.
  • Phil Dahm, Stuart Rosenberg: Intel MCS-48 and UPI-41A Microcontrollers, Reliability Report RR-25, December 1979, Intel Corporation.
  • Microcontroller Handbook, Intel 1984, Order number 210918-002.
  • 8-Bit Embedded Controllers, Intel 1991, Order number 270645-003.
  • UPI-41A User's Manual, Intel 1980, Order number 9800504-02 Rev. B.
  • , October 1993, Order number 231318-006, Intel Corporation.
  • Johan Beaston, Jim Kahn: An 8741A/8041A Digital Cassette Controller, Application Note AP-90, May 1980, Intel Corporation.

External links

  • MCS-48 family architecture
  • Coprolite 8048 Projects
  • Computer History Museum, Intel 8048 Microcontroller Oral History Panel
  • Microcontroller NEC 8741 (image of the Silicium-Chip)
  • HSE-49 Emulator



This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

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