National Instruments Low-Cost Multifunction I/O Board for ISA..., User Manual

Page: 61 / 211

Theory of Operation Chapter 4
Lab-PC+ User Manual 4-2 © National Instruments Corporation
The following are the major components making up the Lab-PC+ board:
• PC I/O channel interface circuitry
• Analog input and data acquisition circuitry
• Analog output circuitry
• Digital I/O circuitry
• Timing I/O circuitry
Data acquisition functions can be executed by using the analog input circuitry and some of the
timing I/O circuitry. The internal data and control buses interconnect the components. The
theory of operation for each of these components is explained in the remainder of this chapter.
The theory of operation for the data acquisition circuitry is included with the discussion of the
analog input circuitry.
PC I/O Channel Interface Circuitry
The PC I/O channel consists of an address bus, a data bus, a DMA arbitration bus, interrupt lines,
and several control and support signals. The components making up the Lab-PC+ PC I/O
channel interface circuitry are shown in Figure 4-2.