The flow control block is designed to IEEE 802.3-2008 specification, clause 31. The MAC can be configured to send pause frames with a programmable pause value and to act on their reception. These two behaviors can be configured asymmetrically.
As an option, an enhanced flow control block designed to IEEE 802.1Qbb Priority Flow Control (PFC) is also available. The MAC can be configured to send PFC frames with programmable enables, pause values, and also act on their reception. The legacy flow control and the priority flow control are mutually exclusive.