Clocking Relationships

The DCMAC Subsystem assumes no phase alignment between any clocks. Any phase is tolerated, even between clocks that are synchronous (in frequency) to each other.

The following table shows the clock frequency relationships in Coupled MAC+PCS mode.

Table 1. Coupled MAC+PCS Mode - Clock Relationships
Mode	AXI-S Width¹	Frequency of Rate Defining Clock (MHz)	Frequency of Related Clocks (MHz) ²	Additional Frequency Relationships
100GE MAC+PCS with and without RS(528,514) FEC	256	tx_serdes_clk = 644.5313 +/- 100 ppm rx_serdes_clk = 644.5313 +/- 100 ppm	tx_core_clk >= 781.25 + 100 ppm rx_core_clk >= 781.25 + 100 ppm tx_axi_clk >= 390.625 + 100 ppm rx_axi_clk >= 390.625 + 100 ppm	tx_axi_clk >= tx_core_clk/2 rx_axi_clk >= rx_core_clk/2
100GE MAC+PCS with and without RS(528,514) FEC	512	tx_serdes_clk = 644.5313 +/- 100 ppm rx_serdes_clk = 644.5313 +/- 100 ppm	tx_core_clk >= 390.625 + 100 ppm rx_core_clk >= 390.625 + 100 ppm tx_axi_clk >= 195.3125 + 100 ppm rx_axi_clk >= 195.3125 + 100 ppm	tx_axi_clk >= tx_core_clk/2 rx_axi_clk >= rx_core_clk/2
100GE MAC+PCS with RS(544,514) FEC 200GE MAC+PCS 400GE MAC+PCS	256	tx_serdes_clk = 664.0625 +/- 100 ppm rx_serdes_clk = 664.0625 +/- 100 ppm	tx_core_clk >= 781.25 + 100 ppm rx_core_clk >= 781.25 + 100 ppm tx_axi_clk >= 390.625 + 100 ppm rx_axi_clk >= 390.625 + 100 ppm	tx_axi_clk >= tx_core_clk/2 rx_axi_clk >= rx_core_clk/2
100GE MAC+PCS with RS(544,514) FEC	512	tx_serdes_clk = 664.0625 +/- 100 ppm rx_serdes_clk = 664.0625 +/- 100 ppm	tx_core_clk >= 390.625 + 100 ppm rx_core_clk >= 390.625 + 100 ppm tx_axi_clk >= 195.3125 + 100 ppm rx_axi_clk >= 195.3125 + 100 ppm	tx_axi_clk >= tx_core_clk/2 rx_axi_clk >= rx_core_clk/2
Bits per 100G. Clocks in this column represent the minimum required frequency. As such, the requirement is +100 ppm minimum (not +/-100 ppm). The clock source must be configured to ensure that even at the lower bound of its operational range (all uncertainties included), the minimum is achieved. These minimum frequencies are based on nominal clock frequencies for other related clocks. If other related clocks are scaled, then clock frequencies in this column must be likewise scaled.

The following table shows the clock frequency relationships for the standalone MAC when running in Independent MAC and PCS+FEC mode.

Table 2. Independent MAC and PCS+FEC Mode - MAC Clock Relationships
Mode	Frequency of Rate Defining Clock (MHz)	Frequency of Related Clocks (MHz)¹	Frequency Relationship to Rate Defining Clock
400G TX Channelized MAC	tx_macif_clk = 260.4167	tx_axi_clk >= 260.4167 tx_core_clk >= 520.8333	tx_axi_clk >= tx_macif_clk tx_core_clk >= 2 x tx_macif_clk
600G TX Channelized MAC	tx_macif_clk = 390.625	tx_axi_clk >= 390.625 tx_core_clk >= 781.25	tx_axi_clk >= tx_macif_clk tx_core_clk >= 2 x tx_macif_clk
400G RX Channelized MAC	rx_macif_clk = 260.4167	rx_axi_clk >= 260.4167 rx_core_clk >= 520.8333	rx_axi_clk >= rx_macif_clk rx_core_clk >= 2 x rx_macif_clk
600G RX Channelized MAC	rx_macif_clk = 390.625	rx_axi_clk >= 390.625 rx_core_clk >= 781.25	rx_axi_clk >= rx_macif_clk rx_core_clk >= 2 x rx_macif_clk
Clocks in this column represent minimum required frequency. As such, the requirement is +100 ppm minimum (not +/-100 ppm). The clock source must be configured to ensure that even at the lower bound of its operational range (all uncertainties included), the minimum is achieved. These minimum frequencies are based on nominal clock frequencies for other related clocks. If other related clocks are scaled, then clock frequencies in this column must be likewise scaled.

The following table shows the clock frequency relationships for the standalone PHY logic when running in Independent MAC and PCS+FEC mode.

Table 3. Independent MAC and PCS+FEC Mode - PHY Clock Relationships
Mode	FLEX I/F Width¹	Frequency of Rate Defining Clock (MHz)	Frequency of Related Clocks (MHz)²
100G PCS with and without RS(528,514) FEC	4x66	tx_serdes_clk = 644.5313 +/- 100 ppm rx_serdes_clk = 644.5313 +/- 100 ppm	tx_flexif_clk >= 390.625 + 100 ppm rx_flexif_clk >= 390.625 + 100 ppm
128GFC³	4x66	tx_serdes_clk = 701.25 +/- 100 ppm rx_serdes_clk = 701.25 +/- 100 ppm	tx_flexif_clk >= 425 + 100 ppm rx_flexif_clk >= 425 + 100 ppm
100G PCS with RS(544,514) FEC 200G PCS 400G PCS	4x66	tx_serdes_clk = 664.0625 +/- 100 ppm rx_serdes_clk = 664.0625 +/- 100 ppm	tx_flexif_clk >= 390.625 + 100 ppm rx_flexif_clk >= 390.625 + 100 ppm
100G PCS with and without RS(528,514) FEC	5x66	tx_serdes_clk = 644.5313 +/- 100 ppm rx_serdes_clk = 644.5313 +/- 100 ppm	tx_flexif_clk >= 322.27⁴ + 100 ppm rx_flexif_clk >= 322.271 + 100 ppm
100G PCS with RS(544,514) FEC	5x66	tx_serdes_clk = 664.0625 +/- 100 ppm rx_serdes_clk = 664.0625 +/- 100 ppm	tx_flexif_clk >= 322.271 + 100 ppm rx_flexif_clk >= 322.271 + 100 ppm
128GFC³	5x66	tx_serdes_clk = 701.25 +/- 100 ppm rx_serdes_clk = 701.25 +/- 100 ppm	tx_flexif_clk >= 340 + 100 ppm rx_flexif_clk >= 340 + 100 ppm
100G FlexO 200G FlexO 400G FlexO	320	tx_serdes_clk = 698.81 +/- 100 ppm rx_serdes_clk = 698.81 +/- 100 ppm	tx_flexif_clk >= 349.40 + 100 ppm rx_flexif_clk >= 349.40 + 100 ppm
100G FEC-only RS(528,514) FEC 2 x 50G FEC-only RS(528,514) FEC	320	tx_serdes_clk = 644.5313 +/- 100 ppm rx_serdes_clk = 644.5313 +/- 100 ppm	tx_flexif_clk >= 322.27⁴ + 100 ppm rx_flexif_clk >= 322.27⁴ + 100 ppm
100G FEC-only RS(544,514) FEC 2 x 50G FEC-only RS(544,514) FEC	320	tx_serdes_clk = 664.0625 +/- 100 ppm rx_serdes_clk = 664.0625 +/- 100 ppm	tx_flexif_clk >= 332.03125 + 100 ppm rx_flexif_clk >= 332.03125 + 100 ppm
Bits per 100G. Clocks in this column represent the minimum required frequency. As such, the requirement is +100 ppm minimum (not +/-100 ppm). +100ppm requirement is only if the flexif clk is not related to the serdes clk. The clock source must be configured to ensure that even at the lower bound of its operational range (all uncertainties included), the minimum is achieved. These minimum frequencies are based on nominal clock frequencies for other related clocks. If other related clocks are scaled, then clock frequencies in this column must be likewise scaled. For transceiver lane serial rate up to 56.42 Gbps. Although the required minimum is 312.5 MHz, the recommended minimum is 322.27 MHz.

Clocking Relationships - 2.3 English

Versal Adaptive SoC 600G Channelized Multirate Ethernet Subsystem (DCMAC) LogiCORE IP Product Guide (PG369)