A 10-bit SMID field is used in the processing system to indicate context for enforcing memory protection. All AXI transactions in PS and CPM are required to carry a 10 bit SMID on A*USER[9:0] signals. This SMID is used by various memory protection elements (XMPU, XPPU) in the PS Interconnect to enforce access privileges. The SMID is applied on these transactions before they enter the Non-Coherent Interconnect. For transactions from CMN:
SMID[9:0] = { 1’b0 , BASE_SMID Register [8:0] }