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Register Map
Register Name
82C55A Register Group
PORTA Register
PORTB Register
PORTC Register
CNFG Register
Interrupt Control Register Group
(PC-DIO-24PnP only)
Register 1
Register 2
Register Description for the 82C55A
© National Instruments Corporation
The following table lists the address map for the PC-DIO-24/PnP.
Table C-1. PC-DIO-24/PnP Address Map
Offset Address
(Hex)
Figure C-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.
Appendix C
Size
00
8-bit
01
8-bit
02
8-bit
03
8-bit
14
8-bit
15
8-bit
C-3
Register-Level Programming
Type
Read-and-write
Read-and-write
Read-and-write
Write-only
Write-only
Write-only
PC-DIO-24/PnP User Manual
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