User manual

Appendix D Register-Level Programming
© National Instruments Corporation D-35 PC-DIO-96/PnP User Manual
; acknowledge the interrupt
ih_0:
mov ax,seg _DATA
mov ds,ax
mov al,eoi ; Signify end of interrupt
cmp slave_ack,0 ; See if we need to acknowledge slave
je short ih_1 ; Jump if not
out acks,al ; Send slave acknowledge
jmp $+2 ; Delay--wait for data transfer
ih_1:
out ackm,al ; Send master acknowledge
; restore saved registers
pop ds
pop ax
sti
iret
_isr_handler endp
_TEXT ends
end
Interrupt Handling
The INTEN bit of Interrupt Register 2 must be set to enable interrupts
from the PC-DIO-96/PnP. This bit must first be cleared to disable
unwanted interrupts. After all sources of interrupts have been disabled
or placed in an inactive state, you can set INTEN.
To interrupt the host computer using one of the 82C55A devices,
program the selected 82C55A for the I/O mode desired. In mode 1, 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 output or input transfers, respectively. The INTE1 and
INTE2 interrupt outputs are cascaded into a single interrupt output for
port A. After interrupts have been enabled from the 82C55A, set the
appropriate enable bit for the selected 82C55A; for example, if you
selected both mode 2 interrupts for PPI C, you would set CIRQ0 in
order to interrupt the host computer.