SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The placement logic is a 2-stage queue which determines the order of commands that run in the DDR controller. The placement logic follows rules for determining placement of new commands into the queue, relative to the contents of the command queue at that time. Placement is determined by considering coherency, address collisions, source collisions, data collisions, user assigned priority, latency, age, and command type to offer low latency for critical masters while optimizing bandwidth for all masters. A second reordering stage allows ready-to-run commands to start even if the head-of-queue command is not yet ready to run. Some of the rules used in the placement logic can be individually enabled or disabled via the DDRSS_CTL_274 through DDRSS_CTL_277 registers. In addition, the queue can be disabled completely, resulting in an in-line queue that services requests in the order that they arrive.
The DDR controller also has a full look-ahead facility that reduces the effect of page misses by pre-conditioning rows for upcoming requests by using “spare” cycles in preceding transactions.