Register-Level Programming Chapter 4
PC-DIO-24 User Manual 4-16 © National Instruments Corporation
Table 4-4. Interrupt Enable Signals for All Mode Combinations
Port A Port A Port B Port B Port A Port A Port B Port A Interrupt
Mode 2 Mode 2 Mode 1 Mode 1 Mode 1 Mode 1 Mode 0 Mode 0 Enable
Output Input Output Input Output Input Bit
No No No No No No Yes Yes N/C
No No No No No Yes Yes No PC6, PC2
No No No No Yes No Yes No PC4, PC2
No No No Yes No No No Yes PC6, PC4
No No No Yes No Yes No No PC6
No No No Yes Yes No No No PC4
No No Yes No No No No Yes PC6, PC4
No No Yes No No Yes No No PC6
No No Yes No Yes No No No PC4
No Yes No No No No Yes No PC2
No Yes No Yes No No No No N/C
No Yes Yes No No No No No N/C
Yes No No No No No Yes No PC2
Yes No No Yes No No No No N/C
Yes No Yes No No No No No N/C
The recommended jumper settings for W1 are as follows.
• PC6 — If port A is in mode 1 input.
• PC4 — If port A is in mode 1 output.
• PC2 — If port A is in mode 2 (port B is not in mode 1).
To enable interrupts from the PC-DIO-24, select PC2, PC4, or PC6 as the active low interrupt
enable signal. Initially, set the selected bit high to disable unwanted interrupts.
Program the PC-DIO-24 for the I/O mode desired. To enable interrupts from the 82C55A, set
either the INTEA or the INTEB bit to enable interrupts from port A or port B, respectively. In
mode 2, set either INTE1 or INTE2 for interrupts on input or output transfers. After interrupts
have been enabled from the 82C55A, clear the selected interrupt enable bit to enable interrupts
from the PC-DIO-24.
An external signal can be used to interrupt the PC-DIO-24 when port A or port B is in mode 0.
Select PC2, PC4, or PC6 as the interrupt enable bit and clear the selected bit to enable interrupts.
Connect the external signal that should trigger an interrupt to either PC3 or PC0. When the
external signal becomes logic high, an interrupt request occurs. To disable the external signal
interrupt, set the selected interrupt enable bit to logic high.