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I have to count modified bits in a volatile 32 bit data word.Example:Initial counter32[32] := 0; olddata := 0x00000010; newdata := 0x0000000001;So we have moddata := newdata xor olddata => moddata := 00000011.So bit0 and bit1 have changed.Now I would have counter[1]++ and counter[0]++;How this can be done on a Cortex-M0+ fastes way?Best regards Juergen
So bit0 and bit1 have changed.Now I would have counter[1]++ and counter[0]++;Sorry for that, ok, I try again…I have to count bit changes in a 32bit data word, separated for each bit.Therefore I have 32 distinct counters in an array named counter32[32].
counter32[0] counts bit changes of bit0, counter32[1] counts bit changes of bit1, and so on.Every time a bit changes, its counter should be incremented.olddata := 0x00000002; newdata := 0x00000001;olddata ^ newdata gives 0x00000011, so two bits changed.Here two bits have changed, bit0 and bit1, so counter32[0]++ and counter32[1]++
Best regardsJuergen
I think something like this.But this is tooo slow for our needs and I have no knowledge of ARM Assembler...MCU is a STM32G0 with Cortex-M0+.
uint32_t counter32[32]; olddata = 0x00000001U; newdata = 0x00000002U; void CountBits(uint32_t old, uint32_t new) { uint32_t x; uint32_t mask = 0x00000001U; int i; x = old ^ new; // x == 0x00000003 for (i = 0; i < 32; i++) { if (x & mask) counter[i]++; mask <<= 1; } } void main (void) { CountBits (olddata, newdata); }