National Instruments AT-DIO-32F, User Manual

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© National Instruments Corporation 3-1 AT-DIO-32F User Manual
Chapter 3
Theory of Operation
This chapter explains the basic operation of the AT-DIO-32F circuitry.
The AT-DIO-32F is a high-speed, 32-bit, parallel, digital I/O interface for the PC. The 32 lines
of digital I/O on the AT-DIO-32F are divided into four 8-bit ports (DIOA, DIOB, DIOC, and
DIOD). Ports A and B are assigned to handshaking Group 1, and Ports C and D are assigned to
handshaking Group 2. Each group can be programmed as either an input or an output group, and
each group has its own independent handshaking signals for data transfers.
The key functional components of the hardware are illustrated in the block diagram shown in
Figure 3-1.
PC AT I/O Channel
I/O Connector
DMA
Control
Circuitry
RTSI
Switch
Data
Latches and
Drivers
Configuration
and Status
Registers
Handshaking
Circuitry
Counters
1, 2, 3
Bus
Transceivers
Address
Decoding
Circuitry
Interrupt
Control
Circuitry
PC I/O
Channel
Control
Circuitry
OUT1, 2
IN1, 2
DIOA
/
8
DIOB
/
8
DIOC
/
8
DIOD
/
8
ACK1, 2
REQ1, 2
RTSI Bus
Figure 3-1. AT-DIO-32F Block Diagram