In some hardware, ref_clk can be input for both the MAC and the PHY. In this
case, setting refclk_cd to None will make the CRG use ref_clk as the RMII
input reference clock:
Pads:
# RMII Ethernet
("eth_clocks", 0,
Subsignal("ref_clk", Pins("D17")),
IOStandard("LVCMOS33"),
),
("eth", 0,
Subsignal("rst_n", Pins("F16")),
Subsignal("rx_data", Pins("A20 B18")),
Subsignal("crs_dv", Pins("C20")),
Subsignal("tx_en", Pins("A19")),
Subsignal("tx_data", Pins("C18 C19")),
Subsignal("mdc", Pins("F14")),
Subsignal("mdio", Pins("F13")),
Subsignal("rx_er", Pins("B20")),
Subsignal("int_n", Pins("D21")),
IOStandard("LVCMOS33")
),
PHY:
self.submodules.ethphy = LiteEthPHYRMII(
clock_pads = self.platform.request("eth_clocks"),
pads = self.platform.request("eth"),
refclk_cd = None)
Thanks @mwick83 for reporting the use case and for the initial implementation.
For correct io delays in nextpnr the DEL_VALUE parameter needs to
be an integer, instead of the "DELAY{}" string.
The use of a "DELAY{}" string appears in the Lattice primitive
manual, but appears to be incorrect. At least based of the current
nextpnr.
Because we are not making use of dynamic io delays here we can
also use the simpler DELAYG block instead of DELAYF.
Fixes#50
This makes clocking more flexible and allows routing on more boards (ex: Pano Logic G2). Since TX clocking
does not need clock phase relationship with the input clock using a combinatorial path is fine.
This makes it Xilinx specific, but without it ISE simplifies this as a single signal
(which is fine) but is not able to keep track of the "keep" attribute of both signals
and fails applying the constraints.
Recent modification that adds S7PLL that in return adds an AsyncResetSynchronizer inside XilinxClocking.
This actually creates a multi-driven net because there is another AsyncResetSync* being added in the Phys.
This change instantiates the PLL without a reset for now, leaving the CD reset intact.
IDELAYE3 requires EN_VTC to be enabled for fixed mode time delay. This eliminates implementation time CRITICAL WARNINGs and ensures generating a bitfile.
