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12.2.6.3 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
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Timer_A SLAU144J–December 2004–Revised July 2013
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