PIO[ABCD] handlers improvement using ATSAM3X8E CLZ instruction #3983
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cmaglie
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agdl
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PIO[ABCD] handlers improvement using ATSAM3X8E CLZ instruction
ollie1400
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May 2, 2022
PIO[ABCD] handlers improvement using ATSAM3X8E CLZ instruction
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This is a small improvement to WInterrupts.c for the DUE which allows a faster interrupt dispatching associated to generic I/O pins.
Basically I have modified the code of the interrupt handler functions PIOA_Handler(), PIOB_Handler(), PIOC_Handler() and PIOD_handler() in the original WInterrupts.c. The improvement consists mainly in taking advantage of ATSAM3XE assembler instruction CLZ. With this instruction it is possible to calculate the number of leading zeros in a 32 bit value in just one machine instruction. CLZ is available in C/C++ using CMSIS function __CLZ(). This change can improve the dispatching of interrupts a lot, specially when you have a sparse number of active interrupts associated with a few i/O pins.