To control advanced transaction behavior the AXI User bits ARUSER and AWUSER are utilized to define a sideband protocol. The format is the same for both ARUSER and AWUSER but differs in available transactions.
The format define several fields as shown in following figure and table. Reserved bits are intended for future extensions.
Op defines the group of operations that are used, Structure selects any structure/layout settings and Sub-op defines a more precise operation, if available.
Currently this functionality is used to provide support for Atomic operations for CCIX and CHI coherency.
The ATS Page defines the group of hints and overrides sideband signals contain page setting information to be used when requesting translations.
The optional PASID sub-field must be applied when PASID is enabled, to allow unique translation for unpropagated Host TA translation requests.