SPU configures the access privileges for a peripheral.
SPU allows configuring access controls individually for each peripheral, and for some peripheral features. For example, a DPPI channel can be configured with different access controls than the peripheral.
SPU controls access according to TrustZone security attributes. If a peripheral or feature is configured as secure, only TrustZone secure accesses are allowed. If a peripheral or feature is configured as non-secure, then accesses are allowed both from secure and non-secure masters.
For some peripherals, the peripheral's DMA has a separate security configuration. If the peripheral is configured as secure, the peripheral's DMA can be configured to perform either secure or non-secure accesses. If the peripheral is configured as non-secure, the peripheral's DMA will always perform non-secure accesses.