What exactly we want to achieve in delay function?

[NitinSaxenait]

Hi, I am going through this discovery book and I have successfully completed it till chapter 8 Leds Again. Now in chapter 9 Clock and timers i was going through these for loop delays using function delay but I am not getting what actually we want to achieve and what this loop is doing in function delay. Can someone please help me with this? I know we are not using delay as we were using it in the previous chapter we have to work with it differently.
This is what I want to understand.
#[inline(never)] fn delay(_tim6: &tim6::RegisterBlock, ms: u16) { **const K: u16 = 3; // this value needs to be tweaked for _ in 0..(K * ms)** { aux9::nop() } }

Okay so I know why we are using nop here I just want to understand the working of constant k & for loop

[sirhcel]

Hello @NitinSaxenait, sections 9 is about shedding some light on the internals of a delay function to give you an impression how it could be implemented. It sketches two common approaches:

• By "counting instructions": looping which does not get optimized away by the compiler
• By "counting timer ticks": setting up a timer and polling its status until it expires

Without any special measures, the compiler will optimize away an empty loop. But it offers a "blessed no operation" which won't: The function aux9::nop resolves to the compiler intrinsic __nop which serves exactly this purpose.

The constant K is the number of loop iterations you have to perform for a millisecond. So K * ms is the number of loop iterations for achieving the desired delay in milliseconds.

[NitinSaxenait]

@sirhcel thanks for the explanation. Now I know what this means.