The ALTPLL IP core allows you to monitor the PLL locking process using a lock signal named
locked
and also allows you to set the PLL to self-reset on loss of lock.
Guideline: Output Clocks
Each MAX 10 PLL supports up to five output clocks. You can use the output clock port as a core output
clock or an external output clock port. The core output clock feeds the FPGA core and the external output
clock feeds the dedicated pins on the FPGA.
The ALTPLL IP core does not have a dedicated output enable port. You can disable the PLL output using
the
areset
signal to disable the PLL output counters.
Guideline: PLL Cascading
Consider the following guidelines when cascading PLLs:
• Set the primary PLL to low bandwidth to help filter jitter. Set the secondary PLL to high bandwidth to
track the jitter from the primary PLL. You can view the Quartus II software compilation report file to
ensure the PLL bandwidth ranges do not overlap. If the bandwidth ranges overlap, jitter peaking can
occur in the cascaded PLL scheme.
Note: You can get an estimate of the PLL deterministic jitter and static phase error (SPE) by using the
TimeQuest Timing Analyzer in the Quartus II software. Use the SDC command
derive_clock_uncertainty
to generate a report titled
PLLJ_PLLSPE_INFO.txt
in your
project directory. Then, use
set_clock_uncertainty
command to add jitter and SPE
values to your clock constraints.
• Keep the secondary PLL in a reset state until the primary PLL has locked to ensure the phase settings
are correct on the secondary PLL.
• You cannot connect any of the
inclk
ports of any PLLs in a cascaded scheme to the clock outputs
from PLLs in the cascaded scheme.
Related Information
PLL Cascading
on page 2-26
UG-M10CLKPLL
2015.06.12
Guideline: Output Clocks
3-3
MAX 10 Clocking and PLL Design Considerations
Altera Corporation
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