Drat, foiled again ! According to the UG578 page 87
"• Near-end PCS Loopback (path 1 in Figure 2-28)
The RX elastic buffer must be enabled and RX_XCLK_SEL must be set to RXDES for
near-end PCS loopback to function properly. While in near-end PCS loopback, the RX
XCLK domain is clocked by the TX PMA parallel clock (TX XCLK). If the RXOUTCLK is used
to clock interconnect logic and RXOUTCLKSEL is set to RXOUTCLKPMA during normal
operation, one of these two items must be changed when placing the GTY transceiver
into near-end PCS loopback:
° Set RXOUTCLKSEL to select RXOUTCLKPCS, or
° Set RXCDRHOLD = 1'b1
• Near-end PMA Loopback (path"
However neither of these controls is brought out to a port or ports on the IP itself.
Where do I go to set one or the other of these? Also, in streaming mode do I need to use NFC to avoid packet loss in these near end loopback modes 1 & 2? I am seeing what looks like 1.6% packet loss.
In a knot,
Loopy Steve
