SPRUIL1D May 2019 – December 2024 DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4VM , TDA4VM-Q1
The Protection Timer is used in conjunction with DL_TC0TXFCThreshold described in Section 12.3.7.5.1.1.1.1. Its purpose is to "protect" the link against the loss of an AFC frame and the resulting stall in communication, if required credits were not delivered.
This timer is running whenever less credits than DL_TC0TCXFCThreshold are available. After expiration, the local UniPro sends an AFC frame to the peer device requesting a credit information update (CReq set to 1). When this AFC request is sent, the timer is restarted. If the peer device does not respond within the second timer period, the link is automatically reinitialized, as the request seems to be lost.
The configuration of the Protection Timer has very little impact on the system performance. If the timer is set to a low value, the amount of AFC request frames may increase (depending on the threshold value). A too high value results in longer periods of inactivity if the link gets broken.
As a consequence setting this timeout value to any value between 512 and 1023 should result in a good compromise between additional AFC frame generation and latency in case of errors:
512 ≤ DL_FC0ProtectionTimeOutVal ≤ 1023;