Cortex-M

SysTick, Power Management

To enable the SysTick feature, use the SysTick control and status registers.When the ENABLE bit of this register is set to 1, the counter begins to operate.In other words, the counter is loaded with a reload value and then the countdown starts.

memory map

The memory map of the Cortex-M3 has some features that are slightly different from the memory map of a typical microcontroller.Some common microcomputers can change the memory area.However, the memory map of Cortex-M3 is a defined memory map, and the address area mapping is fixed.

vector table

The vector table in Cortex-M3 starts at number 0.In a typical microcontroller, the minimum address part (0) of the vector table is assigned a reset vector, but in Cortex-M3, the initial value of the main stack (SP_main) is assigned.

NVIC Register

This section describes the control registers that the NVIC (Nested Vectored Interrupt Controller) has.SysTick-related registers are also included in NVIC registers, which are described in more detail in the SysTick chapter.

interruption

In Cortex-M3, the priority of each interrupt can be changed by the user.It can also be set to 256 levels instead of 8 or 16 levels.The interrupt priority register is used for the setting.

Priority of exceptions

If you read the Cortex-M3 manual, you'll see the words tail-chain, sidestep, and rear-end.This word indicates the timing of exception handling that occurs according to the exception handling priority.A brief explanation of the meaning of each is as follows.

Type of exception

Types of exceptions include resets, interrupts, and faults.The exception handling occurs suddenly. Therefore, it happens asynchronously to the execution of the instruction.However, since only faults are exceptions due to the execution of error conditions due to instruction execution, they basically occur in synchronization with the instruction that caused them.

Endian, memory format, data type, exceptions/interrupts

In Cortex-M3, the endian setting pin BIGEND (Note: It is not a microcontroller pin. (this is the name of the signal line to and from the outside of the logic module).This allows you to choose either the Little Endian or Big Endian format.

Program Status Register(PSR)

The Cortex-M3 has a special register called "Program Status Register (PSR)" that shows the execution status of the program as a special register.The Program Status Register (PSR) represents the system-level processor status and can be divided into three categories