Intel 8051
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The Intel 8051 is a microcontroller (µC) developed by Intel in 1980 for use in embedded products and still (2005) one of the most popular microcontrollers. 8051/8031† cores are used in over 100 devices from more than 20 independent manufacturers such as Dallas, Philips and Atmel. Intel's official designation for the 8051 family of µCs is MCS 51.
The microcontroller is based on a Harvard architecture and although originally designed for single chip microcontroller applications, an expanded mode allows a full 64 KB of external ROM and 64 KB of external RAM to be addressed by means of separate chip select lines for program and register access.
A particular feature of the 8051 microcontroller is the inclusion of a boolean processing engine which allows bit-level boolean logic operations to be carried out directly and efficiently on internal registers and RAM. This has led to the 8051 being popular in industrial control applications and it was widely used in early programmable logic controller (PLC) designs.
Most 8051s include two UARTs, two or three timers, 128-256 bytes of internal ram, 2k-54K of internal program memory, and a simple instruction set. Classically they run at 12 clocks per instruction, and often the clock is near 12MHz so that they run at 1 MIP. Inexpensive systems often use a ceramic resonator instead of a quartz oscillator. If a system needs to remember data over several resets, it may include a serial EEPROM.
The 8051's predecessor, the 8048, was used in the keyboard of the first IBM PC, where it converted keypresses into the serial data stream which is sent to the main unit of the computer. The 8048 and derivatives are still used today for basic model keyboards.
The 8052 is an enhanced version of the 8051 that features:
- 256 bytes of internal RAM, instead of 128
- a third 16-bit timer
- additional Special Function Registers to support the third timer
Notes
(† An 8031 is an 8051 family microcontroller without internal ROM.)
External links
- Microcontroller.com
- 8051 Tutorial (http://www.8052.com/tut8051.phtml) (8052.com)
- Official 8051 FAQ (http://microcontroller.com/Embedded.asp?did=93)
- Intel MCS 51 series microcontrollers (http://www.intel.com/design/mcs51/)
- This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.