SPRUIL1D May 2019 – December 2024 DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4VM , TDA4VM-Q1
A change in DL_TC0TXFCThreshold influences the required level of available credits (1 credit = 32 bytes) in a transmitter before the Protection Timer is started to request an update of credit information.
For example, if this threshold value for TC0 is locally set to 10 credits, the local TX will start the Protection Timer when less than 10 credits are available for sending data to the peer device. If the Protection Timer expires, the local TX sends an AFC0 frame to the peer device with CReq set to 1 to request an update of the peer RX credit information. When the peer device answers with an AFC0 frame at any time, the Protection Timer is restarted if there are still 10 or fewer credits available or stopped otherwise.
This mechanism should prevent that the local TX runs out of credits and needs to stall its data transmissions, when for any reason the credit update was lost or not sent in time.
As a general guideline, this threshold value can be set to its maximum value (1 less than the maximum number of credits of the receive buffer for the corresponding TC, which is stored in the attribute DL_PeerTC0RxInitCreditVal). With this setting the local TX will try to get an update of the local credit information as long as it has not all possible credits available. The overhead for sending the AFC frames depends on the counter value of the Protection Timer, but should not have a negative impact on the link performance.
DLTCxTXFCThreshold = DLPeerTxTXInitCrediVal - 1;