© National Instruments Corporation 1-1 PC-DIO-24 User Manual
Chapter 1Introduction

This chapter 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.

About the PC-DIO-24

Thank you for purchasing the National Instruments PC-DIO-24. The PC-DIO-24 is a low cost,
24-bit parallel, digital I/O interface for the PC. An OKI 82C55A PPI controls the 24 bits of
digital I/O. The 82C55A is very flexible and powerful when interfacing with peripheral
equipment, can operate in either a unidirectional or bidirectional bus mode, and can generate
interrupt request outputs. The 82C55A can be programmed for almost any 8-bit or 16-bit digital
I/O application. All digital I/O is through a standard 50-pin male connector. The pin
assignments for this connector are compatible with standard 24-channel digital I/O applications.
The PC-DIO-24 can be used in a wide range of digital I/O applications. With the PC-DIO-24, a
PC can be interfaced to any of the following.
• Other computers
- Another PC with a National Instruments PC-DIO-24 or AT-DIO-32F
- IBM Personal System/2 with a National Instruments MC-DIO-24 or MC-DIO-32F
- Apple Macintosh II with a National Instruments NB-DIO-24 or NB-DIO-32F
- Any other computer with an 8-bit or 16-bit parallel interface
• Centronics-compatible printers and plotters
• Panel meters
• Instruments and test equipment with BCD readouts and/or controls
• Opto-isolated solid-state relays (SSRs) and I/O module mounting racks
Note: The PC-DIO-24 cannot sink sufficient current to drive the SSR-OAC-5 and
SSR-OAC-5A output modules. However, it can drive the SSR-ODC-5 output module
and all SSR input modules available from National Instruments.
If you need to drive a SSR-OAC-5 or SSR-OAC-5A, you can either use a non-inverting
digital buffer chip between the PC-DIO-24 and the SSR backplane, or you can use a
DIO-23F or MIO Series board with appropriate connections (e.g., SC-205X and
cables).