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PLL Reconfiguration/Phase Problem

Altera_Forum
Honored Contributor II
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I'm using a Cyclone IV, Quartus 13.1.0, and have designed a reconfigurable PLL that can be programmed for one of four different output frequencies. There are two PLL outputs, FAST & SLOW, the SLOW output is 1/2 the frequency of the FAST output. The problem I'm seeing is that when I reconfigure the PLL the phase relationship between FAST & SLOW is sometimes incorrect, it should be zero. It appears to jump in increments of 1/2 the FAST clock period. Has anyone ever seen this?

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Altera_Forum
Honored Contributor II
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Just wonder if you have try to reset the PLL after the reconfiguration? Reset is recommended after reconfiguration to ensure the PLL can function as expected.

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Altera_Forum
Honored Contributor II
432 Views

if initial (pre-reconfig) phase shift for both FAST & SLOW is 0 degree, then whatever MNC counter you reconfigure, expected that you will get a 0 degree phase relationship after a RESET. 

what is your initial settings and what did you reconfig? Perhaps i can help you further.
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