Resets - 3.1 English

UltraScale+ Devices Integrated 100G Ethernet Subsystem Product Guide (PG203)

Document ID
PG203
Release Date
2022-11-02
Version
3.1 English

The integrated CMAC block has a total of 12 resets. They are TX_RESET , RX_RESET , and RX_SERDES_RESET[9:0] . During configuration TX_RESET , RX_RESET and RX_SERDES_RESET[9:0] need to be asserted High and after the clocks are stable, the resets are released. During normal operation the RX and TX paths can be asserted independently. Within the RX and TX logic paths, there are separate resets to the core and the lane logic. The reset procedure is simple and the only requirement is that a reset must be asserted until the corresponding clock(s) are stable. The 100G Ethernet IP core takes care of ensuring that the different resets are properly synchronized to the required domain. It is up to you to ensure a reset is held until the corresponding clock is fully stable.

The 100G Ethernet IP core provides sys_reset input to reset GTs and integrated CMAC block and gtwiz_reset_tx_datapath and gtwiz_reset_rx_datapath to reset GT and CMAC RX and TX datapaths individually.

Note: Some of the control inputs to the 100G Ethernet IP core can only be modified while the core is held in reset. If one of these inputs needs changing, the appropriate RX or TX LBUS reset input ( RX_RESET or TX_RESET ) must be asserted until the control input is stabilized. All resets within the block are asynchronously asserted, and synchronously deasserted. Standard cell synchronizers are used, where applicable per guidelines to synchronize assertion and release of resets to respective clock inputs.

See This Figure and This Figure for diagrams of the clocking and resets. The available modes are based on the Vivado® Integrated Design Environment (IDE) selection and configuration. For Asynchronous mode, TXOUTCLK sources the TXUSRCLK, and RXOUTCLK sources the RXUSRCLK. Asynchronous Mode allows per specification PPM difference between clocks.

Figure 3-1: CMAC Clocking and Reset – Asynchronous Clock Mode, Multi Lane (Multi Lane is RX GT Buffer Mode Enabled)

X-Ref Target - Figure 3-1

X18950-cmac-async-clock-mode-multi.jpg
Figure 3-2: CMAC Clocking and Reset – Asynchronous Clock Mode, Single Lane (Single Lane is RX GT Buffer Mode Bypassed)

X-Ref Target - Figure 3-2

X18955-cmac-async-clock-mode-single.jpg