PIC microcontrollers: Difference between revisions

Revision as of 14:43, 9 December 2005

Revision as of 14:44, 9 December 2005

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Microchip Technology does not use PIC as an acronym; in fact the brand name is PICmicro. It is generally regarded that PIC stands for Peripheral Interface Controller, although General Instruments' original acronym for the PIC1650 was "Programmable Intelligent Computer".

The original PIC was built to be used with smelly GI's new 16-bit [[Central processing unit|CPU]], the CP1600. While generally a good CPU, the CP1600 had poor [[I/O]] performance, and the 8-bit PIC was developed in 1975 to improve performance of the overall system by offloading I/O tasks from the CPU. The PIC used simple [[microcode]] stored in [[Read-only memory|ROM]] to perform its tasks, and although the term wasn't used at the time, it is a [[RISC]] design that runs one instruction per cycle (4 oscillator cycles).

In 1985 GI spun off their microelectronics division, and the new ownership cancelled almost everything — which by this time was mostly out-of-date. The PIC, however, was upgraded with [[EPROM]] to produce a programmable [[channel controller]], and today a huge variety of PICs are available with various on-board peripherals (serial communication modules, [[UART]]s, motor control kernels, etc.) and program memory from 512 words to 32k words and more (a "word" is one assembly language instruction, varying from 12, 14 or 16 bits depending on the specific PICmicro family).