The program counter (PC) is a register that is part of the central processing unit (CPU). It contains the memory address for the next instruction that has to be executed during the instruction cycle of the microprocessor. Principle of Operation Each instruction cycle begins by accessing the instruction stored at the address that is pointed by [...]
Overview Speaking in general a bootloader is any piece of code that is executed before the main application code starts. In this article we will focus on a particular type of a bootloader - one that is used to erase the code of the main application from the flash memory and program it with a [...]
Writing programs for embedded systems often requires the manipulation of individual bits. Below is a list of the most common operations. In the examples we are performing them on an unsigned long variable called ctrl_reg. Setting a bit We can set a bit using the bitwise OR operator (|): ctrl_reg |= 1UL << n; The [...]
Overview There are two major types of memory system architectures when it comes to executing code in embedded systems: Execute in Place (XIP): The program code is executed directly from a flash memory. Store and Download (SnD) : The program code is stored in a non-volatile memory but is copied to RAM during the boot up [...]
Hardware memory is used for storing information. In the case of embedded systems that may be the program data ,the program code itself, event logging etc. There are many types of technologies used when creating memory cells and many ways to categorize them, but we can distinguish two major categories based on the memory reaction [...]
Exceptions are events that disrupt the normal execution flow of the program. When an exception occurs the processor handles it by usually executing dedicated piece of code called exception handler. Each type of exception can have its own exception handler. In some literature sources exceptions and interrupts are analyzed as two different things. Expeptions being [...]
A breakpoint is an intentional stopping place during an execution of a program. It is a powerful debugging feature allowing us to suspend the execution of the program at a certain point and examine the current values of variables and memory locations. The program can then be resumed from the exact point it was suspended. Adding or removing breakpoints [...]
We can generally define three levels of abstraction from the underlying hardware when we develop embedded programs: Machine Code Assembly Language High Level Language Machine code is the native language of the microprocessors (but it is not used for directly writing programs). So no matter at what level of abstraction we decide to write our [...]
There are two main concepts that have to be explained in order for us to fully understand the differences between global and local variables in C programs: Scope - determines the region of the program where a variable can be accessed Storage Duration - determines when a variable is created and destroyed (lifetime of the variable) [...]
The memory layout of C programs consists of several segments. The segments accessible to a user program are shown in the figure below: Fig. 1 C program memory layout Code Segment (.text) This segment stores the executable program code (the machine instructions). Variables defined with the const type qualifier can also be placed [...]