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. The 8048 is probably the most prominent member of the family. Initially, this family was produced using NMOS (n-type metal–oxide–semiconductor) technology. In the early 1980s, it became available in CMOS technology. It was 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. Though the MCS-48 series was eventually replaced by the very successful MCS-51 series, it remained quite popular even by the year 2000 due to its low cost, wide availability, memory-efficient one-byte instruction set, and mature development tools. Because of this, it is used in high-volume, cost-sensitive consumer electronics devices such as TV remotes, computer keyboards, and toys. 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 microcontroller's oscillator block divides by three and then further divides the result into five machine states. With its 11 MHz maximum crystal, one gets 0.73 MIPS (of single-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. The MCS-48 series was commonly used in computer and terminal keyboards, converting key presses into protocols that can be understood by digital circuits. This also allows the possibility of serial communication, reducing the amount of conductors needed in cables on external keyboards. Microprocessors had been used in keyboards since at least 1972, simplifying earlier discrete designs. The 8048 has been used in this application since its introduction in 1978.

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Computer keyboard

A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Replacing early punched cards and paper tape technology, interaction via teleprinter-style keyboards have been the main input method for computers since the 1970s, supplemented by the computer mouse since the 1980s. Keyboard keys (buttons) typically have a set of characters engraved or printed on them, and each press of a key typically corresponds to a single written symbol.

Protected mode

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Intel MCS-48

EE-208: Microcontrollers and digital systems

Microcontrôleurs et conception de systèmes numériques couvre le fonctionnement interne d'un microcontrôleur, des notions de base d'architecture de processeur et de système informatique ainsi que les i