© National Instruments Corporation xi PC-DIO-24 User Manual
About This Manual

This manual describes the mechanical and electrical aspects of the PC-DIO-24 and contains
information concerning its operation and programming. The PC-DIO-24 is a 24-bit parallel,
digital I/O interface designed around an 82C55A programmable peripheral interface (PPI). The
PC-DIO-24 is a member of the National Instruments PC Series of PC I/O Channel expansion
boards for the IBM PC computer family. These boards are designed for low-cost data acquisition
and control for applications in laboratory testing, production testing, and industrial process
monitoring and control.
This manual describes installation, basic programming considerations, and theory of operation
for the PC-DIO-24. The example programs included are written in C.

Organization of This Manual

The PC-DIO-24 User Manual is organized as follows:
• Chapter 1, Introduction, describes the PC-DIO-24, lists what you need to get started,
describes software programming choices, optional equipment, and custom cables, and
explains how to unpack the PC-DIO-24.
• Chapter 2, Configuration and Installation, describes how to configure and install the
PC-DIO-24, including I/O connector signal descriptions, handshake timing diagrams, and
cabling instructions.
• Chapter 3, Theory of Operation, contains a functional overview of the PC-DIO-24 board and
explains the operation of each functional unit making up the PC-DIO-24.
• Chapter 4, Register-Level Programming, describes in detail the address and function of each
of the PC-DIO-24 control and status registers. This chapter also includes important
information related to register-level programming the PC-DIO-24.
• Appendix A, Specifications, lists the specifications for the PC-DIO-24 board.
• Appendix B, I/O Connector, describes the pinout and signal names for the I/O connector on
the PC-DIO-24.
• Appendix C, OKI 82C55A Data Sheet, contains the manufacturer data sheet for the
OKI 82C55A (OKI Semiconductor) CMOS programmable peripheral interface. This
interface is used on the PC-DIO-24 board.
• Appendix D, Customer Communication, contains forms you can use to request help from
National Instruments or to comment on our products.
• The Glossary contains an alphabetical list and description of terms used in this manual,
including abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms.