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SD16 Operation
21-17SD16
SD16 Interrupt Handling Software Example
The following software example shows the recommended use of SD16IV and
the handling overhead. The SD16IV value is added to the PC to automatically
jump to the appropriate routine.
The numbers at the right margin show the necessary CPU cycles for each
instruction. The software overhead for different interrupt sources includes
interrupt latency and return-from-interrupt cycles, but not the task handling
itself. The latencies are:
- SD16OVIFG, CH0 SD16IFG, CH1 SD16IFG 16 cycles
- CH2 SD16IFG 14 cycles
The interrupt handler for channel 2 SD16IFG shows a way to check
immediately if a higher prioritized interrupt occurred during the processing of
the ISR. This saves nine cycles if another SD16 interrupt is pending.
; Interrupt handler for SD16.
INT_SD16 ; Enter Interrupt Service Routine 6
ADD &SD16IV,PC; Add offset to PC 3
RETI ; Vector 0: No interrupt 5
JMP ADOV ; Vector 2: ADC overflow 2
JMP ADM0 ; Vector 4: CH_0 SD16IFG 2
JMP ADM1 ; Vector 6: CH_1 SD16IFG 2
;
; Handler for CH_2 SD16IFG starts here. No JMP required.
;
ADM2 MOV &SD16MEM2,xxx ; Move result, flag is reset
... ; Other instruction needed?
JMP INT_SD16 ; Check other int pending 2
;
; Remaining Handlers
;
ADM1 MOV &SD16MEM1,xxx ; Move result, flag is reset
... ; Other instruction needed?
RETI ; Return 5
;
ADM0 MOV &SD16MEM0,xxx ; Move result, flag is reset
RETI ; Return 5
;
ADOV ... ; Handle SD16MEMx overflow
RETI ; Return 5