EM357-RTR datasheet(28/240 Pages) ETC2

28 / 240 page

EM351 / EM357

ARM

® CortexTM-M3 and Memory Modules

This chapter discusses the ARM

® CortexTM-M3 Microprocessor, and reviews the EM35x’s flash and RAM memory

modules as well as the Memory Protection Unit (MPU).

5.1

ARM

Cortex

TM-M3 Microprocessor

The EM35x integrates the ARM

® CortexTM-M3 microprocessor, revision r1p1, developed by ARM Ltd., making the

EM35x a true System-on-Chip solution. The ARM

® CortexTM-M3 is an advanced 32-bit modified Harvard

architecture processor that has separate internal program and data buses, but presents a unified program and

data address space to software. The word width is 32 bits for both the program and data sides. The ARM

CortexTM-M3 allows unaligned word and half-word data accesses to support efficiently-packed data structures.

The ARM

® CortexTM-M3 clock speed is configurable to 6 MHz, 12 MHz, or 24 MHz. For normal operation 24 MHz

is preferred over 12 MHz due to improved performance for all applications and improved duty cycling for

applications using sleep modes. The 6 MHz operation can only be used when radio operations are not required

since the radio requires an accurate 12 MHz clock.

The ARM

® CortexTM-M3 in the EM35x has also been enhanced to support two separate memory protection

levels. Basic protection is available without using the MPU, but normal operation uses the MPU. The MPU

allows for protecting unimplemented areas of the memory map to prevent common software bugs from

interfering with software operation. The architecture could also allow for separation of the networking stack

from the application code using a fine granularity RAM protection module. Errant writes are captured and

details are reported to the developer to assist in tracking down and fixing issues.

5-1

120-035X-000D

Preliminary

EM357-RTR 数据表(PDF) 28 Page - List of Unclassifed Manufacturers