Pause Operation - 3.0 English - PG314

Versal Devices Integrated 100G Multirate Ethernet MAC Subsystem Product Guide (PG314)

Document ID
PG314
Release Date
2024-11-13
Version
3.0 English

The MRMAC subsystem provides a comprehensive mechanism for pause packet termination and generation. The TX and RX have independent interfaces for processing pause information as described in this section.

The subsystem is capable of handling 802.3x and priority-based pause operation. The RX path parses pause packets and presents the extracted quanta on the status interface. The TX path can accept pause packet requests from the control interface and inject the requested packets into the data stream. Both global pause packets and priority-based pause packets are handled.

When both pause_req and pause_ack signals are asserted, there might be a slight variation in the total time due to internal resynchronization of pause interface signals with the core clock and a dependency on the actual bit time on the clock frequency of the serdes interface (which is impacted by the ppm error on the recovered clock). The synchronization error is noticeable for small quantas, while the ppm error is more pronounced for large quantas. For small quantas, you might experience an error of approximately three quanta times due to clock synchronization.

Note: 802.3x and global pause are used interchangeably throughout the document.