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Chapter 3
Core Overview
3.1 ARM Cortex-M0+ core introduction
The enhanced ARM Cortex M0+ is the member of the Cortex-M Series of processors
targeting microcontroller cores focused on very cost sensitive, low power applications. It
has a single 32-bit AMBA AHB-Lite interface and includes an NVIC component. It also
has hardware debug functionality including support for simple program trace capability.
The processor supports the ARMv6-M instruction set (Thumb) architecture including all
but three 16-bit Thumb opcodes (52 total) plus seven 32-bit instructions. It is upward
compatible with other Cortex-M profile processors.
3.1.1 Buses, interconnects, and interfaces
The ARM Cortex-M0+ core has two bus interfaces:
• Single 32-bit AMBA-3 AHB-Lite system interface that provides connections to
peripherals and all system memory, which includes flash memory and RAM
• Single 32-bit I/O port bus interfacing to the GPIO with 1-cycle loads and stores
3.1.2 System tick timer
The CLKSOURCE field in SysTick Control and Status register selects either the core
clock (when CLKSOURCE = 1) or a divide-by-16 of the core clock (when
CLKSOURCE = 0). Because the timing reference is a variable frequency, the TENMS
field in the SysTick Calibration Value Register is always 0.
3.1.3 Debug facilities
This device supports standard ARM 2-pin SWD debug port.
Freescale Semiconductor, Inc.
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
49
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