Single-board microcontroller

A single-board microcontroller is a microcontroller built onto a single printed circuit board. This board provides all of the circuitry necessary for a useful control task: a microprocessor, I/O circuits, a clock generator, RAM, stored program memory and any necessary support ICs. The intention is that the board is immediately useful to an application developer, without requiring them to spend time and effort to develop controller hardware.

As they are usually low-cost, and have an especially low capital cost for development, single-board microcontrollers have long been popular in education. They are also a popular means for developers to gain hands-on experience with a new processor family.

Single-board microcontrollers appeared in the late 1970s, when the appearance of early microprocessors, such as the 6502 and the Z80, made it practical to build an entire controller on a single board, as well as affordable to dedicate a computer to a relatively minor task.

In March 1976, Intel announced a single-board computer product that integrated all of the support components required for their 8080 microprocessor, along with 1 kilobyte of RAM, 4 kilobytes of user-programmable ROM, and 48 lines of parallel digital I/O with line drivers. The board also offered expansion through a bus connector, but could be used without an expansion card cage when applications did not require additional hardware. Software development for this system was hosted on Intel's Intellec MDS microcomputer development system; this provided assembler and PL/M support, and permitted in-circuit emulation for debugging.

Processors of this era required a number of support chips to be included outside of the processor. RAM and EPROM were separate, often requiring memory management or refresh circuitry for dynamic memory. I/O processing might have been carried out by a single chip such as the 8255, but frequently required several more chips.

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