Register-Level Programming Chapter 4
Lab-NB User Manual 4-60 © National Instruments Corporation
Port C status-word bit definitions for input (port A and port B):
76543210
I/O I/O IBFA INTEA INTRA INTEB IBFB INTRB
Bit Name Description
7, 6 I/O Extra I/O status lines when port A is in mode 1 input.
5 IBFA Input Buffer Full for Port A—High indicates that data has been
loaded into the input latch for port A.
4 INTEA Interrupt Enable Bit for Port A—Enables interrupts from the
82C55A for port A. Controlled by setting or resetting of PC4.
3 INTRA Interrupt Request Status for Port A—When INTEA is high and
IBFA is high, this bit is high, indicating that an interrupt request is
asserted.
2 INTEB Interrupt Enable Bit for Port B—Enables interrupts from the
82C55A for port B. Controlled by setting or resetting PC2.
1 IBFB Input Buffer Full for Port B—High indicates that data has been
loaded into the input latch for port B.
0 INTRB Interrupt Request Status for Port B—When INTEB is high and
IBFB is high, this bit is high, indicating that an interrupt request is
asserted.
At the digital I/O connector, port C has the following pin assignments when in mode 1 input.
Notice that the status of STBA* and STBB* is not provided in the port C status word.
PC7
PC6
PC5
PC4
PC3
PC2
PC1
PC0
I/O
IBFA
STBA*
INTRA
STBB*
IBFB
INTRB
I/O
Group A
Group B