Texas Instruments MSP430x1xx, User Manual

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ADC12 Operation
17-19 ADC12
ADC12 Interrupt Handling Software Example
The following software example shows the recommended use of ADC12IV
and the handling overhead. The ADC12IV 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:
-
ADC12IFG0 - ADC12IFG14, ADC12TOV and ADC12OV 16 cycles
-
ADC12IFG15 14 cycles
The interrupt handler for ADC12IFG15 shows a way to check immediately if
a higher prioritized interrupt occurred during the processing of ADC12IFG15.
This saves nine cycles if another ADC12 interrupt is pending.
; Interrupt handler for ADC12.
INT_ADC12 ; Enter Interrupt Service Routine 6
ADD &ADC12IV,PC; Add offset to PC 3
RETI ; Vector 0: No interrupt 5
JMP ADOV ; Vector 2: ADC overflow 2
JMP ADTOV ; Vector 4: ADC timing overflow 2
JMP ADM0 ; Vector 6: ADC12IFG0 2
... ; Vectors 8-32 2
JMP ADM14 ; Vector 34: ADC12IFG14 2
;
; Handler for ADC12IFG15 starts here. No JMP required.
;
ADM15 MOV &ADC12MEM15,xxx ; Move result, flag is reset
... ; Other instruction needed?
JMP INT_ADC12 ; Check other int pending
;
; ADC12IFG14-ADC12IFG1 handlers go here
;
ADM0 MOV &ADC12MEM0,xxx ; Move result, flag is reset
... ; Other instruction needed?
RETI ; Return 5
;
ADTOV ... ; Handle Conv. time overflow
RETI ; Return 5
;
ADOV ... ; Handle ADCMEMx overflow
RETI ; Return 5