Unaligned memory access is the access of data with a size of N number of bytes from an address that is not evenly divisible by the number of bytes N. If the address is evenly divisible by N, we have aligned memory access. We can express this as Address/N, where Address is the memory address
To better understand the concept of little-endian and big-endian formats we first have to look at how memory is accessed. The memory space of a microprocessor is expected to be byte-addressable. When a CPU has a 32-bit address bus this means that it can access a total of 232 addresses each with a size of
Real-time operating systems (RTOS) allows us to develop complex embedded systems. By using self-contained tasks (threads) each with their own context we can implement programs with multitasking behavior using a single CPU. Passing information between these tasks (inter-task communication) is an important aspect when designing an embedded application using an RTOS. We can say that
The peripheral access layer is a layer of the firmware that provides access to the registers of a microcontroller's peripheral units. It has to be easy to use, well structured, and efficient. This layer is part of the software packages every microcontroller vendor provides for free with their Software Development Kits (SDK) and Integrated Development
Direct Memory Access (DMA) is a process of transferring data from one memory location to another without the direct involvement of the processor (CPU). The main benefit of using DMA is more efficient data movement in the embedded system. Principle of Operation There are many different types of DMA implementations, some of them for very
Designing an embedded system that employs a real-time operating system (RTOS) with multitasking behavior means that there will be resources that must be shared between the tasks. These shared resources (e.g peripheral modules, data structures, communication interfaces, etc.) by their nature do not support multiple concurrent accesses. Accessing them without any rules in place may
This article is a natural extension on the topics we covered in Function Calls on ARM Cortex-M Microprocessors. Due to the hardware specifics of the Cortex-M architecture, there is actually a lot of common in how function calls and exceptions are handled. The good thing for us as developers is that all exception handlers can
In our article covering the scheduling algorithms of real-time operating systems (RTOS), we stated that they can run tasks in such a way that leaves the impression of a multitasking behavior. This is achieved by giving the RTOS the capability to interrupt a currently executing task and to start executing another one. At some point
We already introduced the basic concepts of real-time operating systems (RTOS) and now we will take a deeper look into one of the most important things when designing an embedded system using an RTOS - the scheduling of the tasks and the algorithms that are used. Scheduling Process Scheduling is the process of deciding which
Embedded systems are microcontroller-based systems that are designed to perform specific functions such as reading sensor data, responding to external events, communicating with other systems, controlling processes, etc. The tricky part is to make the distinction of what exactly qualifies such a system as real-time. Aren't all embedded systems operating in real-time? In order for
