EM357-RTR datasheet(34/241 Pages) SILABS

34 / 241 page

Rev 1.3

5.2.3. Registers

Appendix A, Register Address Table provides a short description of all application-accessible registers within the

EM35x. Complete descriptions are provided at the end of each applicable peripheral’s description. The registers

are mapped to the system address space starting at address 0x40000000. These registers allow for the control

and configuration of the various peripherals and modules. The CPU only performs word-aligned accesses on the

system bus. The CPU performs a word aligned read-modify-write for all byte, half-word, and unaligned writes and a

word-aligned read for all reads. Silicon Labs recommends accessing all peripheral registers using word-aligned

addressing.

As with the RAM, the peripheral registers fall within an address range that allows for bit-band access by the ARM®

CortexTM-M3, but the standard MPU configuration does not allow access to this alias address range.

5.3. Memory Protection Unit

The EM35x includes the ARM® CortexTM-M3 Memory Protection Unit, or MPU. The MPU controls access rights

and characteristics of up to eight address regions, each of which may be divided into eight equal sub-regions.

Refer to the ARM® CortexTM-M3 Technical Reference Manual (DDI 0337A) for a detailed description of the MPU.

Ember software configures the MPU in a standard configuration and application software should not modify it. The

configuration is designed for optimal detection of illegal instruction or data accesses. If an illegal access is

attempted, the MPU captures information about the access type, the address being accessed, and the location of

the offending software. This simplifies software debugging and increases the reliability of deployed devices. As a

consequence of this MPU configuration, accessing RAM and register bit-band address alias regions is not

permitted, and generates a bus fault if attempted.

EM357-RTR Datasheet(PDF) 34 Page - Silicon Laboratories