The following describes the receive clocks in the MRMAC.
-
rx_serdes_clk[3:0]
- This GT SerDes clock is used to drive data across the SerDes interface to the MRMAC.
-
rx_core_clk[3:0]
- This is the internal high-speed clock which drives the bulk of the MRMAC receive datapath. This per-port clock is typically shared
with the
tx_serdes_clk
, but depending on the application it can be derived from therx_serdes_clk
. -
rx_alt_serdes_clk[3:0]
- This is an internally-used clock derived from the primary SerDes
clocks. These clocks run at exactly 1/2 the
rx_serdes_clk[3:0]
frequencies. The logic and hook-ups for this clock are typically generated by the IP Wizard.
-
rx_flexif_clk[3:0]
- This is used by the flex interface. When the Flex I/F is active and
in a multi-lane mode (that is, data rate > 25G),
rx_flexif_clk[N]
must operate at a frequency ≥ 1/2 of the correspondingrx_core_clk[N]
frequency. When the flex interface is in a single lane mode (25G or 10G), it must run at a frequency ≥ 1/2 of the correspondingrx_serdes_clk[N]
frequency.
-
rx_axi_clk[2][0]
- This is a per-port AXI clock. In addition to clocking the RX
AXI4-Stream interface in independent clocking mode, the
rx_axi_clk[2][0]
clocks are also used only to clock certain statistics and flow control signals. Therx_axi_clk[2][0]
clocks must operate at a frequency high enough to maintain the desired data rate across the AXI4-Stream bus, which meansrx_axi_clk[N]
must be greater than or equal to 1/2 of the correspondingrx_core_clk[N]
(orrx_serdes_clk[N]
in 10GE or 25GE mode) frequency.
-
rx_ts_clk[3:0]
- This clock drives the 1588 timestamping signaling. The MRMAC timestamp timers attempt to synchronize with the external time-of-day source which is running on this clock.