Better delay description

CC #236

Signed-off-by: Daniel Egger <[email protected]>

Author: therealprof

src/asm.rs

@@ -26,13 +26,16 @@ pub fn bkpt() {
 
 /// Blocks the program for *at least* `n` instruction cycles
 ///
-/// This is implemented in assembly so its execution time is the same regardless of the optimization
-/// level.
+/// This is implemented in assembly so its execution time is independent of the optimization
+/// level, however it is dependent on the specific architecture and core configuration.
 ///
-/// NOTE that the delay can take much longer if interrupts are serviced during its execution.
+/// NOTE that the delay can take much longer if interrupts are serviced during its execution 
+/// and the execution time may wary with other factors. This delay is mainly useful for simple
+/// timer-less initialisation of peripherals iff accurate timing is not essential. In any other
+/// case please use more accurate methods to cause a delay.
 #[inline]
 pub fn delay(_n: u32) {
-    // NOTE(divide by 4) is easier to compute than `/ 3` is it's just a shift (`>> 2`).
+    // NOTE(divide by 4) is easier to compute than `/ 3` because it's just a shift (`>> 2`).
     match () {
         #[cfg(all(cortex_m, feature = "inline-asm"))]
         () => unsafe {