Query in multiple clockdomain

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Ramesh Reddy

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Hi all,

Whenever there is going to be transactions b/w 2 clock
domain, irrespective of the clock's speed you need to
synchronize them. Here synchronizer is needed to
avaoid the metastable states in the machine, which can
be caused due to 2 different clcok-tree's flop's
direct talking .

thanks in advance...

ramesh reddy
 

the best way is use fifo and read a one clock speed and write at another clock speed..

ensure that no fifo full occurs..


Regards
Shankar
 

Some cases:

Case 1: Single signal crossing clock domains, toggling slowly (i.e. not a pulse).
Use 2 flip-flops to re-time it into the new clock domain

Case 2: Single signal crossing clock domains, pulsing for 1 clock cycle in the original domain.
Convert the pulse into a toggled signal, pass the toggled signal through the clock boundary, re-time with 2 flip-flops, re-convert back into a pulse.

Case 3: Parallel data.
Use a FIFO.
 

Hi,
in this document, there is a section on getting asynchronous inputs and how to use handshake signals to prevent metastability. this should solve any problems of multi-clock domains.
 

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