Peripheral Interface Adapter
Encyclopedia
The Peripheral Interface Adapter (PIA) is a peripheral
integrated circuit
providing parallel I/O interfacing capability for microprocessor
systems. 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 DIP package
.
The PIA is designed for glueless connection to the Motorola 6800
style bus
, and provides 20 I/O lines, which are organised into 2 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.
It was used in Atari 800 family of computers (to provide four joystick ports to the machine). It was also used in the Apple I to interface the ASCII keyboard and the display.
Peripheral
A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
providing parallel I/O interfacing capability for microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
systems. Common PIAs include the Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
MC6820 and MC6821, and the MOS Technology
MOS Technology
MOS Technology, Inc., also known as CSG , was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor, and various designs for Commodore International's range of home computers.-History:MOS Technology, Inc...
MCS6520, all of which are functionally identical but have slightly different electrical characteristics. The PIA is most commonly packaged in a 40 pin DIP package
Dual in-line package
In microelectronics, a dual in-line package is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board or inserted in a socket.A DIP is usually referred to as a DIPn, where n is...
.
The PIA is designed for glueless connection to the Motorola 6800
Motorola 6800
The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips...
style bus
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
, and provides 20 I/O lines, which are organised into 2 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.
It was used in Atari 800 family of computers (to provide four joystick ports to the machine). It was also used in the Apple I to interface the ASCII keyboard and the display.