©
National Instruments Corporation 4-1 PC-DIO-24/PnP U ser Manual
Chapter
4
Theory of Operation
This chapter contains a functional overview of the PC-DIO-24/PnP
board and explains the operation of each functional unit making up the
PC-DIO-24/PnP.

Functional Overview

The block diagram in Figure 4-1 illustrates the key functional
components of the PC-DIO-24/PnP board.
Figure 4-1. PC-DIO-24/PnP Block Diagram
The PC I/O channel consists of an address bus, a data bus, interrupt
lines, and several control and support signals. Control and data transfers
to the system microprocessor are asynchronous.
I/O Connector
Interrupt
Control
Circuitry
82C55A
PPI
Bus
Transceivers
/
8
/
8
/
8
+5 V
PC I/O Channel
1 A Fuse
PA
PB
PC
PC3
PC0
Bus Interface
(Plug and Play)
Address
Decode Interrupt
Circuitry