Why does digitalWrite HIGH vs digitalWrite LOW take different amounts of time?

i got oscilloscope , fun, thought i'd put quick sketch toggle output fast loop run on uno.

code: [select]


#define jpin  8

void setup() {
  pinmode(jpin, output);
}

void loop() {
  static int = 0;
 
  if(i++ & 1)
    digitalwrite(jpin, low);
  else
    digitalwrite(jpin, high);
}


i found high time longer low time. thought maybe processing of "if" conditional might make difference swapped high/low , still high signal 3 times longer low signal averaging 11.5us high , 3.7us low above code regardless.

is there that's inherently more difficult / time consuming raise vs lower signal? 3x timing difference pretty significant. haven't looked low level programming on uno see how control registers modified there seems wrong.

oscilloscopes r fun!  

try:

void loop()
{

digitalwrite( jpin, !digitalread(jpin) );

}

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