Jameco Electronics Rabbit 3000 - Manual (Page 109)

100 Rabbit 3000 Microprocessor
7.10.2 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 #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
;
OPP IP ; get back entry priority
IPRES ; restore interrupted routine’s priority
RET ; return from interrupt
Table 7-16. Control Registers for External Interrupts
Reg Name Reg Address Bits 7,6 Bits 5,4 Bits 3,2 Bits 1,0
I0CR 10011000 xx INT0B PE4 INT0A PE0 Enb INT0
I1CR 10011001 xx INT1B PE5 INT1A PE1 Enb INT1
edge triggered
00-disabled
10-rising
01-falling
11-both
edge triggered
00-disabled
10-rising
01-falling
11-both
interrupt
00-disable
01-pri 1
10-pri 2
11-pri 3