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Contents
PC-DIO-24/PnP User Manual vi
©
National Instruments Corporation
Digital I/O Power-up State Selection ........................................................................... 3-7
High DIO Power-up State.............................................................................. 3-7
Low DIO Power-up State............................................................................... 3-9
Timing Specifications................................................................................................... 3-10
Mode 1 Input Timing..................................................................................... 3-12
Mode 1 Output Timing .................................................................................. 3-13
Mode 2 Bidirectional Timing......................................................................... 3-14
Chapter 4
Theory of Operation
Functional Overview .................................................................................................... 4-1
Bus Transceivers............................................................................................ 4-2
Bus Interface .................................................................................................. 4-2
Interrupt Control Circuitry............................................................................. 4-2
82C55A Programmable Peripheral Interface................................................. 4-2
Digital I/O Connector..................................................................................... 4-3
Appendix A
Specifications
Appendix B
OKI 82C55A Data Sheet
Appendix C
Register-Level Programming
Introduction .................................................................................................................. C-1
Register Map ................................................................................................................ C-3
Register Description for the 82C55A............................................................. C-3
Register Description for the Interrupt Control Registers............................... C-5
Interrupt Control Register 1 (PnP Board Only)............................... C-6
Interrupt Control Register 2 (PnP Board Only)............................... C-7
Programming Considerations for the 82C55A............................................................. C-8
Modes of Operation for the 82C55A ............................................................. C-8
Mode 0............................................................................................. C-8
Mode 1............................................................................................. C-8
Mode 2............................................................................................. C-9
Single Bit Set/Reset Feature............................................................ C-9
Mode 0—Basic I/O........................................................................................ C-9
Mode 0 Programming Example....................................................... C-10