uint32 s, e, d, cyc;
// 1ms = 16000 count
cyc = 1000 / sToCoNet_AppContext.u16TickHz;
cyc *= 16000;
// check the process time
s = u32AHI_TickTimerRead();
.. some process ..
e = u32AHI_TickTimerRead();
// calculate the time
if (e > s) {
d = e - s;
} else {
d = 64000 - e + s;
}
d /= 16; // now `d' represents micro sec.