SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
The Sum of Blocks Total rule is an extremely aggressive global control that sets and clears PFC triggers on receive ports due to conditions in all transmit FIFOs regardless of receive traffic. When any priority has a trigger condition set, all receive ports will trigger PFC for that priority. The intent of this rule is to shutdown lower priorities with jumbo packets as the total switch congestion increases.
A PFC priority is triggered by conditions in all transmit FIFO by the below equation at any time:
priX_trig_set = sum of all tx FIFO blocks allocated in all ports >= thresh_setX[4:0]
A PFC priority is cleared when conditions in all transmit FIFO’s satisfy the below equation at any time:
priX_trig_clr = sum of all tx FIFO blocks allocated in all ports <= thresh_clrX[4:0]
Where,