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 1990's 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 instructions are single byte/cycle ones, but a large amount of opcodes 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).
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 original IBM PC keyboard used an 8048 as its internal microcontroller. 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. 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.
- MCS-48 MICROCOMPUTER USER'S MANUAL, 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.
- Microprocessor Peripherals UPI-41A/41AH/42/42AH User's Manual, 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.
- 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
- Datasheet (pdf) Philips MAB8400-Family
- "Korg Poly-61 Service Manual".
- Gordon Reid (November, 2004). "The History Of Roland, Part 1: 1930–1978". The History Of Roland. Sound On Sound Magazine. Retrieved 29 November 2010.
- "Section 4: Keyboard", Technical Reference: Personal Computer, Personal Computer Hardware Reference Library (Revised ed.), IBM, April 1984
- "Section 1: System Board", Technical Reference: Personal Computer AT, Personal Computer Hardware Reference Library, IBM, September 1985