Peripheral Interface Adapter: Difference between revisions

Revision as of 18:46, 25 June 2017

Revision as of 08:51, 28 December 2017

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Common PIAs include the [[Motorola]] MC6820 and MC6821, and the [[MOS Technology]] MCS6520, all of which are functionally identical but have slightly different electrical characteristics. The PIA is most commonly packaged in a 40 pin [[Dual in-line package|DIP package]].

The PIA is designed for glueless connection to the [[Motorola 6800]] style [[Computer bus|bus]], and provides 20 I/O lines, which are organised into 2two 8-bit bidirectional ports (or 16 general-purpose I/O lines) and 4 control lines (for handshaking and interrupt generation). The directions for all 16 general lines (PA0-7, PB0-7) can be programmed independently. The control lines can be programmed to generate interrupts, automatically generate handshaking signals for devices on the I/O ports, or output a plain high or low signal.

In 1976 Motorola switched the MC6800 family to a depletion-mode technology to improve the manufacturing yield and to operate at a faster speed. The Peripheral Interface Adapter had a slight change in the electrical characteristics of the I/O pins so the MC6820 became the MC6821. <ref name = "MC6821">{{Cite book | title = Advanced Information: 1.5 and 2.0 MHz Components for the M6800 Microcomputer System. | pages = 4–6 | publisher = Motorola Semiconductor Products | ___location = Austin, Texas | date = April 1977 | id = ADI-429}} The MC6820 became the MC6821 because the electrical characteristic of PA0–7 and PB0–7 pins changed slightly. The typical Input High Current went from -250 μAdc to -400 μAdc and the Input Low Current went from 1.0 mAdc to 1.3 mAdc.</ref>

The MC6820 was used in the Apple I to interface the ASCII keyboard and the display.<ref>

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and Kiss.<ref>

{{Cite book | title = Kiss Manual | pages = 22 | date = 1979| publisher = Bally | url = http://www.ipdb.org/machine.cgi?id=1386}}</ref>

The MCS6520 was used in [[Atari 400]]/[[Atari 800]] and [[Commodore PET]] family of computers (for example, to provide four joystick ports to the machine).<ref>

{{Cite book | title = Sams Computerfacts Technical Service Data - Atari 800 | page = IV | date = November 1984 | url=http://www.atarimania.com/documents/Sams_Computer_facts_Atari_800.pdf}}</ref>

The [[Tandy Color Computer]] used two MC6821s to provide I/O access to the video, audio and peripherals.

==References==