SPRUJ52C june 2022 – july 2023 AM69 , AM69A , TDA4AH-Q1 , TDA4AP-Q1 , TDA4VH-Q1 , TDA4VP-Q1
Real-time and non-real-time transactions are an example of transactions that should, ideally, have orthogonal processing, so it is important that they are allocated in separate way groups to take advantage of per-way-group hazarding.
In addition to having a configurable number of cache way groups be backed with data,MSMC also provides software control over the number of cache way groups real time and non-real time transactions are each allowed to allocate into. The DATABACKED_GROUPS fields within the RT_WAY_SELECT and NRT_WAY_SELECT memory-mapped registers control the number of data backed way groups to be allocatable by real-time and non-real-time transactions, respectively. Similarly, the NON_DATABACKED_GROUPS fields within the RT_WAY_SELECT and NRT_WAY_SELECT memory-mapped registers control the number of way groups without data backing that can be allocated by real-time and non-real-time transactions, respectively.
For any setting of these values MSMC will minimize the number of way groups that are simultaneously allocatable by both real-time and non-real-time transactions. For example, if there are 3 way groups with data backing and both real-time and non-real-time transactions are configured to be allocateable in 2 data backed way groups, then one way group will be allocateable by only real-time transactions, one only by non-realtime transactions, and one that is allocateable by both real-time non-real-time transactions. This is shown in Figure 8-5.
If DATABACKED_GROUPS is set to ‘0’ or is a value greater than the value in the CACHE_SIZE field within the CACHE_CTRL memory mapped register, then MSMC defers to the CACHE_SIZE setting to determine what way groups are available for any data-allocating transactions. Similarly, if NON_DATABACKED_GROUPS is set to ‘0’ or is a value greater than the value of (8-CACHE_SIZE), then MSMC defers to (8- CACHE_SIZE) when determining what way groups are available for any non-data-allocating transactions.