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Chapter 3
Hardware Overview
DAQCard-DIO-24 User Manual
3-2
©
National Instruments Corporation
port A and port B use some or all of the port C lines as handshaking
control lines. You can configure port B for mode 0 or 1, and port A for
mode 0, 1, or 2.
PC Card I/O Channel Interface Circuitry
The PC Card I/O channel consists of an address bus, a data bus,
interrupt lines, and several control and support signals. The PC Card I/O
channel interface circuitry consists of an address decoder, data buffers,
interrupt controller circuitry, timing interface circuitry, a card
information structure, and PC Card control registers. The components
making up the DAQCard-DIO-24 PC Card I/O channel interface
circuitry are shown in Figure 3-2.
Figure 3-2.
PC Card I/O Channel Interface Circuitry Block Diagram
When the card is inserted, the software selects the interrupt level that
the DAQCard-DIO-24 uses. Two software-controlled registers
determine which events, if any, generate interrupts. You can program
the 82C55A to generate interrupt requests by setting PC3 for group A
or PC0 for group B. When interrupts are enabled for group A, an active
PC I/O Channel
Data
Buffers
Interrupt
Control
Data Bus
IRQ
Address Bus
Address
Decoder
Register Selects
Data Bus
PC Card I/O Channel
Timing
Interface
Control Lines
Card
Information
Structure
PC Card
Control
Registers
PC0 (IRQ)
PC3 (IRQ)
Read and Write Signals (Control)
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