Timing, Timing -3 – National Instruments DAQCard-1200 User Manual

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Chapter 4

Theory of Operation

4-3

When you first insert the card into your computer, the system examines
information stored in the DAQCard-1200 Card Information Structure
(CIS). This data is used to configure the card appropriately for the system
in which it is used. When the system has assigned the card to a section of
memory, it updates the PC Card control registers and initializes the card.

The rest of the circuitry consists of address decoders, data buffers,
I/O channel interface timing control circuitry, and interrupt control
circuitry.

Timing

The DAQCard-1200 uses two 82C53 counter/timer integrated circuits for
internal data acquisition and DAC timing and for general-purpose
I/O timing functions. Figure 4-3 shows a block diagram of both groups of
timing circuitry (counter groups A and B).