User’s Manual 87
7.9.2 Interrupt Vectors: INT0 - EIR,0x00/INT1 - EIR,0x08
When it is desired to expand the number of interrupts for additional peripheral devices, the
user should use the interrupt routine to dispatch interrupts to other virtual interrupt rou-
tines. Each additional interrupting device will have to signal the processor that it is
requesting an interrupt. A separate signal line is needed for each device so that the proces-
sor can determine which devices are requesting an interrupt.
The following code shows how the interrupt service routines can be written.
; External interrupt Routine #1
int1:
IPRES ; restore system priority
RET ; return and ignore interrupt
;
; External interrupt Routine #0 (programmed priority could be 3)
int2:
PUSH IP ; save interrupt priority
IPSET 1 ; set to priority really desired (1, 2, etc.)
; insert body of interrupt routine here
;
POP IP ; get back entry priority
IPRES ; restore interrupted routine’s priority
RET ; return from interrupt
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