Appendix D Register-Level Programming
PC-DIO-96/PnP User Manual
D-4
©
National Instruments Corporation
Register Descriptions
The register descriptions for the devices on the PC-DIO-96/PnP,
including the 82C55A, the 82C53, and each of the interrupt control
registers, are given on the pages that follow.
Register Description for the 82C55A
Figure D-1 shows the two control word formats used to completely
program the 82C55A. The control word flag determines which control
word format is being programmed. When the control word flag is 1,
bits 6 through 0 select the I/O characteristics of the 82C55A ports.
These bits also select the mode in which the ports are operating (that is,
mode 0, mode 1, or mode 2). When the control word flag is 0, bits 3
through 0 select the bit set/reset format of port C.
Содержание PC-DIO-96/PnP
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