Appendix B
Register-Level Programming — Port C Status-Word Bit Definitions for Input (Ports A and B)
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National Instruments Corporation
B-21
PCI-DIO-96/PXI-6508/PCI-6503 User Manual
Port C Status-Word Bit Definitions for Input (Ports A and B)
Address:
Base a 02 (hex) for PPI A
Base a 06 (hex) for PPI B
Base a 0A (hex) for PPI C
Base a 0E (hex) for PPI D
Type:
Read and write
Word Size:
8-bit
Bit Map:
Bit
Name
Description
7–6
I/O
Input/Output—These bits can be used for general-purpose
I/O when port A is in mode 1 input. If these bits are
configured for output, the port C bit set/reset function
must be used to manipulate them.
5
IBFA
Input Buffer Full for Port A—A high setting indicates that
data has been loaded into the input latch for port A.
4
INTEA
Interrupt Enable Bit for Port A—Setting this bit enables
the INTRA flag from port A of the 82C55A. Control
INTEA by setting/resetting PC4.
3
INTRA
Interrupt Request Status for Port A—This status flag,
which operates only when INTEA is high, indicates that
port A has acquired data and is ready to be read. If you
have enabled interrupts (by setting INTEN and the
appropriate bit in Interrupt Control Register 2), this status
flag also indicates that an interrupt request is pending for
port A.
2
INTEB
Interrupt Enable Bit for Port B—Setting this bit enables
the INTRB flag from port B of the 82C55A. Control
INTEB by setting/resetting PC2.
1
IBFB
Input Buffer Full for Port B—A high setting indicates that
data has been loaded into the input latch for port B.
7
6
5
4
3
2
1
0
I/O
I/O
IBFA
INTEA
INTRA
INTEB
IBFB
INTRB