Timer, t1-t0, integral promotion

For ARM7, A hardware timer is 32-bits, and unsigned int is 32-bits too;
For a 16-bits MCU, A hardware timer is 16-bits, and unsigned int is 16-bits too;

So,

t0 = timer_val;
while ( ( timer_val - t0 ) < delay_val );

provide a simple and good delay;

Not so sure about, if a cast is needed.

t0 = timer_val;
while ( (unsigned int)( timer_val - t0 ) < delay_val );

Just noticed that, due to the integral promotion,

unsigned short t0, t1;
( t1 - t0 ) is a signed int.

It seems that,

unsigned int t0, t1;
( t1 - t0 ) is still an unsigned int.

I noticed this, because I use unsigned short to present a 16-bits timer_val on my X86-PC for testing/simulating purpose, and the result is not what I expected.