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Altera_Forum
Honored Contributor
Honored ContributorDynamic phase reconfiguration of ALTPLL in Cyclone IV
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.5 Replies
Altera_ForumLook 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--- 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--- 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--- 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
With Cyclone III and IV, I see phase_done one slightly smaller than one scanclk cycle, means the handbook is basically correct.
