Chadderz121 / bakingpi-www

Website for Baking Pi: Operating Systems Development tutorial (Raspberry Pi)
Other
404 stars 114 forks source link

OK04 Questions #33

Open seesoonki opened 4 years ago

seesoonki commented 4 years ago

Very new to asm coding. Puzzled why systemTimer.s Wait loop$ uses: sub elapsed,r0,start to delay?

Q1. Isn't GetTimeStamp 64bit, but SUB 32-bit? Q2. Why is it ok to ignore r1 counter values and only subtract on r0?