Dynamic phase reconfiguration of ALTPLL in Cyclone IV

Question

I am trying to dynamically control the phase of a clock signal by using an ALTPLL.

Generated a the ALTPLL with phase control signals, but I have not been able to find a detailed description of the signals, timing diagrams or design examples. The ALTPLL IP Core User Guide does not contain much.

Signals that I need more information on are:

Input [2:0] phasecounterselect

Input phaseupdown

Input phasestep

Input scanclk

Output locked

Output phasedone

Does anybody have more information on this.

altera_forum · Answer

Look at the description that starts on page 5-39 in the Cyclone IV handbook:  https://www.altera.com/en_us/pdfs/literature/hb/cyclone-iv/cyclone4-handbook.pdf  There's a nice waveform on page 5-41.

altera_forum · Answer

--- Quote Start ---

Look at the description that starts on page 5-39 in the Cyclone IV handbook:

https://www.altera.com/en_us/pdfs/literature/hb/cyclone-iv/cyclone4-handbook.pdf

There's a nice waveform on page 5-41.

--- Quote End ---

Thanks, exactly what I was looking for.

altera_forum · Answer

--- Quote Start ---

Thanks, exactly what I was looking for.

--- Quote End ---

I have generated an ALT PLL with phase control. When simulating I discovered that the phasedone signal does not behave as stated in Cyclone IV handbook. According to the handbook; the phasedone signal goes inactive (low) for one clock cycle of scanclk when changing phase. Simulations show that phasedone only goes inactive(low) for half a clock cycle of scanclk. I imagine that the simulation shows the behaviour of a model of the PLL hardware block in the FPGA, which leaves me with the question: Do I believe the simulation or the handbook?

altera_forum · Answer

--- Quote Start ---

Simulations show that phasedone only goes inactive(low) for half a clock cycle of scanclk. I imagine that the simulation shows the behaviour of a model of the PLL hardware block in the FPGA, which leaves me with the question: Do I believe the simulation or the handbook?

--- Quote End ---

Expect that phasedone can be processed in a state machine running at scanclk, keeping the handbook timing specification.

altera_forum · Answer

With Cyclone III and IV, I see phase_done one slightly smaller than one scanclk cycle, means the handbook is basically correct.

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Dynamic phase reconfiguration of ALTPLL in Cyclone IV

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