SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
The Tx Per Channel Buffers implement a FIFO for each Tx DMA channel that is used for buffering packet control and payload data that has been fetched by the Tx Packet DMA units. The buffers are byte oriented on write so that the data from the DMA units which may not be full words can be packed properly. The buffers are block oriented on read and each Tx (source) channel in the PKTDMA controller maps directly onto a thread in the Tx PSI interface. The Tx Per Channel Buffer block outputs queue fullness information to the Tx Scheduler block which it then uses to determine when it should initiate DMA opportunities to backfill the buffers. The Tx Per Channel Buffer will initiate transfers to the target whenever any data is available in each channel buffer and credits are available in the corresponding thread. The block will simultaneously monitor the status of all of the threads and will perform a round robin arbitration between the different threads for the use of the Transmit PSI-L interface. Each thread for which the target is indicating it can accept data and which currently has data available in the channel buffer will be included in the arbitration.