Intel MCS-48


The MCS-48 microcontroller 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 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.
Though the MCS-48 series was eventually replaced by the very popular MCS-51 series, even at around year 2000 it remained 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.

Variants

The 8049 has 2 KB of masked ROM 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. 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.
The Intel 8748 has 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.
DeviceInternalMemoryRemarks
80201K × 8 ROM64 × 8 RAMsubset of 8048, 20 pins, only 13 I/O lines
80211K × 8 ROM64 × 8 RAMsubset of 8048, 28 pins, 21 I/O lines
80222K × 8 ROM64 × 8 RAMsubset of 8048, A/D-converter
8035none64 × 8 RAM
8039none128 × 8 RAM
8040none256 × 8 RAM
80481K × 8 ROM64 × 8 RAM
80492K × 8 ROM128 × 8 RAM
80504K x 8 ROM256 × 8 RAM
87481K × 8 EPROM64 × 8 RAM
87492K × 8 EPROM128 × 8 RAM
87P50ext. ROM socket256 × 8 RAMHas piggy-back socket for 2758/2716/2732 EPROM.
86481K × 8 OTP EPROM64 × 8 RAMfactory OTP EPROM

DeviceInternalMemoryRemarks
80411K × 8 ROM64 × 8 RAMUniversal Peripheral Interface
8041AH1K × 8 ROM128 × 8 RAMUPI
8741A1K × 8 EPROM64 × 8 RAMUPI, EPROM version of 8041
8741AH1K × 8 OTP EPROM128 × 8 RAMUPI, OTP EPROM version of 8041AH
8042AH2K × 8 ROM256 × 8 RAMUPI
87422K × 8 EPROM128 × 8 RAMUPI, EPROM version
8742AH2K × 8 OTP EPROM256 × 8 RAMUPI, OTP EPROM version of 8042AH

Uses

The Tandy/Radio Shack TRS-80 Model II, released in 1979, used the 8021 in its keyboard. The 8021 allowed the Model II to be the first desktop computer system with a separate detachable lightweight keyboard connected with by a single thin flexible wire, and likely the first keyboard to use a dedicated microprocessor, both attributes that would be copied years later by Apple and IBM. The 8021 processor scans the key matrix, converts switch closures to an 8-bit code and then transmits that code serially to the keyboard interface on the main system. The 8021 will also accept commands to turn indicator LEDs on or off. This was all done with just four chips, a remarkable feat at the time. The 8021 was also used in the keyboards for the TRS-80 Model 12, 12B, 16, 16B and the Tandy 6000/6000HD.
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 gating function for the AT's Intel 80286 CPU and could be commanded by software to reset the 80286. Later PC compatibles integrate the 8042's functions into their super I/O devices.
The 8048 was used in the Magnavox Odyssey² video game console, the Korg Trident series, the Korg Poly-61, Roland Jupiter-4 and Roland ProMars analog synthesizers. The Sinclair QL used the closely related Intel 8049 to manage its keyboard, joystick ports, RS-232 inputs and audio.
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.

Derived microcontrollers

Philips Semiconductors 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 Compact Disc players.

Literature

;MCS-48
;UPI-41