Texas Instruments MSP430x1xx manual Taiv Software Example

Timer_A Operation

TAIV Software Example

The following software example shows the recommended use of TAIV and the handling overhead. The TAIV 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:

- Capture/compare block TACCR0	11 cycles
- Capture/compare blocks TACCR1, TACCR2	16 cycles
- Timer overflow TAIFG	14 cycles

;	Interrupt handler for TACCR0 CCIFG.		Cycles
CCIFG_0_HND
;	...	; Start of handler Interrupt latency 6
	RETI		5

; Interrupt handler for TAIFG, TACCR1 and TACCR2 CCIFG.

TA_HND	...		; Interrupt	latency	6
	ADD	&TAIV,PC	; Add offset to Jump table		3
	RETI		; Vector 0: No interrupt		5
	JMP	CCIFG_1_HND	; Vector 2: TACCR1		2
	JMP	CCIFG_2_HND	; Vector 4: TACCR2		2
	RETI		; Vector 6: Reserved		5
	RETI		; Vector 8: Reserved		5
TAIFG_HND			; Vector 10: TAIFG Flag
	...		; Task starts here
	RETI				5
CCIFG_2_HND			; Vector 4: TACCR2
	...		; Task starts here
	RETI		; Back to main program		5
CCIFG_1_HND			; Vector 2: TACCR1
	...		; Task starts here
	RETI		; Back to main program		5

11-18Timer_A