Embedded Processor Hardware

- details about the basics of the processing unit hardware within an embedded system, their architecture operation and a tutorial about the technology used.

Microprocessors and microcontrollers can generically be termed forms of microcomputer.

The microcomputer is essentially the engine behind any form of embedded system or even larger stand-alone computers.

Embedded processor definition

The embedded processor can be defined as a small, relatively inexpensive computing unit with a microprocessor or microcontroller as its central processing unit. It also includes memory, and input/output (I/O) facilities.

Embedded processor basics

Whatever the form of computer, the basic processing engine is essentially the same. It consists of a number of elements, each performing different functions to enable the overall microcomputer to operate.

Block diagram showing a basic embedded processor unit comprising he central processing unit, RAM, ROM and IO.
Basic embedded processor unit block diagram

The main elements within a computer or embedded processing engine include:

  • Processor / CPU:   The processor or more correctly the central processing unit is the circuit block where the logical processing is undertaken. It allows addition subtraction and other functions to be undertaken.
  • Read only memory, ROM:   The ROM is typically used for the storage of a programme. In larger computers it is used for the storage of the boot programme, but in embedded processors and computing systems it is sued for the storage of all the programme. Unlike RAM, a ROM is a permanent form of storage that does not lose its content when the power is removed. Some forms of ROM are re-programmable and the programme data can be updated when the correct conditions are set. This form of ROM is called a programmable read only memory or PROM.
  • Random access memory, RAM:   The RAM elements of the embedded processor are used for temporary storage of programme data or instructions. The data can be written to the RAM at any time, and an important feature of the processor RAM is that it loses its date when the power is removed. RAM comes in two forms - static and dynamic.

    • Dynamic RAM:   Dynamic RAM is used within a processor of any form, and also an embedded processor. It is the primary form of RAM used and is used to store the majority of the data. It is more dense than static RAM, but is slower than static RAM.
    • Static RAM:   This form of RAM is used with some processors, especially within computers for cache memory - memory that is used for frequently access data. It is faster than dynamic RAM but less dense.
  • Interface:   The interface or I/O which stands for Input / Output is the way in which the overall computer interacts with the outside world.
  • Data bus:   The data bus is the data bus, consisting of several lines that is used to pass data long. The data bus is typically used to send complete bytes of data at a time, i.e. bit parallel and byte serial. As such systems require the number of lines equal to the number of bytes in each byte. Thus typically data bus widths may be 4, 8, 16, 32 64 bits wide dependent upon the system.

The processor hardware for the embedded system can take many physical forms. It may be a small microcontroller based system set up for a specific task where only a small amount or processing is required, or it may be a larger microprocessor based system capable of undertaking much more exacting tasks. Whatever the requirements, the embedded processor will have the same basic structure and the same basic circuit blocks.

By Ian Poole

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