[moved] How gray coding solve metastabiltiy issues ?

[Ltarek]

How gray coding solve metastabiltiy issues ?

Thanks

 

[KlausST]

Re: How gray coding solve metastabiltiy issues ?

Hi,

I think it doesn't solve the problem but it reduces the error to max 1 LSB.

Klaus

 

[FvM]

Re: How gray coding solve metastabiltiy issues ?

it reduces the error to max 1 LSB

It allows consistent transfer of numeric values (e.g. counters) between asynchronous clock domains if the value changes only by an unit at a time.

 

[asdf44]

Re: How gray coding solve metastabiltiy issues ?

To add, take the transition of 7 (0111) to 8 (1000). During that transition every bit is changing and in a real life design the exact order that the receiver of those bits receives them may be random. So for example the receiver might see the MSB change first meaning it briefly sees 15 (1111) before the lower 3 bits change to zeros making the value 8. If the receiver is asynchronous from the transmitter it might take action based on that incorrect value of 15.

As said, with gray coding only 1 bit changes at a time and that one bit can only ever mean the difference of one LSB. So even if there is a meta-stability issue the only uncertainty is whether the receiver gets the correct value or the value which was correct just a couple nanoseconds before and it can't get any value other than those two.