Forum Discussion
Honored ContributorPLL Reconfiguration/Phase Problem
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?
2 Replies
Altera_ForumJust 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.
- Altera_Forum
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.
