Appendix B
Register-Level Programming — Port C Status-Word Bit Definitions for Output (Ports A and B)
PCI-DIO-96/PXI-6508/PCI-6503 User Manual
B-24
ni.com
Port C Status-Word Bit Definitions for Output (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
OBFA*
Output Buffer Full for Port A—A low setting indicates
that the CPU has written data to port A.
6
INTEA
Interrupt Enable Bit for Port A—Setting this bit enables
the INTRA flag from port A of the 82C55A. Control this
bit by setting/resetting PC6.
5–4
I/O
Input/Output—These bits can be used for general-purpose
I/O when port A is in mode 1 output. If these bits are
configured for output, you must use the port C bit set/reset
function to manipulate them.
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 this
bit by setting/resetting PC2.
1
OBFB*
Output Buffer Full for Port B—A low setting indicates
that the CPU has written data to port B.
7
6
5
4
3
2
1
0
OBFA*
INTEA
I/O
I/O
INTRA
INTEB
OBFB*
INTRB