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kasli: don't pass rtio pll feedback through bufg 

UG472: "The MMCM performance increases because the
feedback clock is not subjected to noise on the core supply since it
never passes through a block powered by this supply."

Signed-off-by: Robert Jördens <rj@quartiq.de>
This commit is contained in:
Robert Jördens 2018-11-06 11:58:55 +00:00
parent b6e4961b0f
commit ba4bf6e59b
1 changed files with 7 additions and 4 deletions
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11
artiq/gateware/targets/kasli.py
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@ -44,7 +44,7 @@ class _RTIOCRG(Module, AutoCSR):
pll_locked = Signal()
rtio_clk = Signal()
rtiox4_clk = Signal()
ext_clkout_clk = Signal()
fb_clk = Signal()
self.specials += [
Instance("PLLE2_ADV",
p_STARTUP_WAIT="FALSE", o_LOCKED=pll_locked,
@ -57,13 +57,16 @@ class _RTIOCRG(Module, AutoCSR):
# VCO @ 1.5GHz when using 125MHz input
p_CLKFBOUT_MULT=12, p_DIVCLK_DIVIDE=1,
i_CLKFBIN=self.cd_rtio.clk,
i_CLKFBIN=fb_clk,
i_RST=self._pll_reset.storage,
o_CLKFBOUT=rtio_clk,
o_CLKFBOUT=fb_clk,
p_CLKOUT0_DIVIDE=3, p_CLKOUT0_PHASE=0.0,
o_CLKOUT0=rtiox4_clk),
o_CLKOUT0=rtiox4_clk,
p_CLKOUT1_DIVIDE=12, p_CLKOUT1_PHASE=0.0,
o_CLKOUT1=rtio_clk),
Instance("BUFG", i_I=rtio_clk, o_O=self.cd_rtio.clk),
Instance("BUFG", i_I=rtiox4_clk, o_O=self.cd_rtiox4.clk),