126.96.36.199. TX Flow Control
Before a TLP can be transmitted, flow control logic verifies that the link partner's RX port has sufficient buffer space to accept it. The TX Flow Control interface reports the link partner's available RX buffer space to the Application. It reports the space available in units called Flow Control credits for posted, non-posted and completion TLPs (as defined in the RX Flow Control section).
TX credit limit signals are provided in a TDM manner similar to how the RX credit limit signals are provided.