1.2.3 Receive Buffer

The transaction layer contains an 8-KB receive buffer to accept incoming TLPs from the link and send them to the application layer for processing. The receive buffer stores TLPs based on the transaction type (posted, non-posted, or completion). A transaction always has a header but does not always have data. The receive buffer accounts for this distinction, maintaining separate resources for the headers and data for each type of transaction. For completion transactions, data (CPLD) TLPs are stored in the received buffer in the 64-bit addressing format, with each outstanding AXI4 slave read request consuming 16 credits (totaling 128 bytes), and the headers and data consuming one credit each (totaling 16 bytes).