User manual

National Instruments Corporation D-1 PC-DIO-96/PnP User Manual

Programming

Appendix

This appendix describes in detail the address and function of each of the

PC-DIO-96/PnP control and status registers. This appendix also

includes important information about register-level programming on

the PC-DIO-96/PnP along with program examples written in C and

assembly language.

Note: If you plan to use a programming software package such as

LabWindows/CVI or NI-DAQ with your PC-DIO-96/PnP board, you need

not read this appendix.

Introduction

Note: You can configure your PC-DIO-96/PnP board to use base addresses in the

range of 100 to 3E0 hex. Your PC-DIO-96/PnP board occupies 16 bytes of

address space and must be located on a 16-byte boundary. Therefore, valid

addresses include 100, 110, 120..., 3E0 hex. The base I/O address is

software configured and does not require you to manually change any

settings on the board. For more information on configuring the

PC-DIO-96PnP, see Chapter 2, Installation and Configuration.

The three 8-bit ports of the 82C55A are divided into two groups of 12

signals each: group A and group B. One 8-bit control word selects the

mode of operation for each group. The group A control bits configure

port A (A7 through A0) and the upper 4 bits (nibble) of port C (C7

through C4). The group B control bits configure port B (B7 through B0)

and the lower nibble of port C (C3 through C0). These configuration

bits are defined in the Register Description for the 82C55A section later

in this appendix. Because there are four 82C55A PPI devices on the

board, they are referenced as PPI A, PPI B, PPI C, and PPI D when

differentiation is required.

The three 16-bit counters of the 82C53 are accessed through individual

data ports and controlled by one 8-bit control word. The control word

selects how the counter data ports are accessed and what mode the