EMBEDDED COMPUTER

SYSTEMSUBMITTED BY: GOVIND KAINTURA

MCA 1ST YEAR

EMBEDDED-SYSTEMA SYSTEM IN WHICH THE COMPUTER (GENERALLY A MICROCONTROLLER OR MICROPROCESSOR) IS INCLUDED AS AN INTEGRAL PART OF THE SYSTEM. OFTEN, THE COMPUTER IS RELATIVELY INVISIBLE TO THE USER, WITHOUT OBVIOUS APPLICATIONS, FILES, OR OPERATING SYSTEMS.

EXAMPLES OF PRODUCTS WITH INVISIBLE EMBEDDED SYSTEMS ARE THE CONTROLLER THAT RUNS A MICROWAVE OVEN OR THE ENGINE CONTROL SYSTEM OF A MODERN AUTOMOBILE.

1) A/D converter:  A hardware device that reads an analog signal—

typically a voltage—compares it to a reference signal, and converts the resulting percentage to a digital value. 

2) ABEL (Advanced Boolean Expression Language): A design language for creating the logic to be

implemented in a simple programmable logic device. Programs created with ABEL are compiled into the binary pattern necessary to create the PLD with a device programmer. 

3) Address bus : A set of wires connected to a processor and all of the peripherals with which it communicates, for the purpose of selecting a specific memory location or register within a particular peripheral. If the address bus contains n electrical lines, the processor can address up to 2n unique locations. Address decoding logic between the processor and the devices connected to the bus select the proper device, typically based on the uppermost bits.

4) Active low : Denotes a logic device or circuit where a logic 1 is a lower

voltage than a logic 0.

5) Aliasing : Allowing one memory location or register to be accessible at

more than one address. Aliasing is a result of address decoding and often happens with peripheral control and status registers. 

For example, if an I/O device has just four byte-wide registers but is mapped into a 256-byte region of memory, aliasing will occur. In this case, the same four registers can be read or written at any of 64 different locations within that region.

6) Analog: Analog is the way the world beyond the quantum level

works. Part of the challenge of digital engineering is to convert noisy, inaccurate, and ugly real-world data to the pristine purity of 1s and 0s. The last two decades have seen a massive growth in digital signal processors, partly because they allow us to replace analog circuits with digital. Ultimately, the goal is to push the digital components all the way back to all systems' front ends--essentially connecting a radio's antenna, for example, directly into a DSP input.

7) Anode: The element of a semiconductor device that accepts

electrons. In a diode, for example, current passes from the anode to the cathode. On a diode, the anode is the terminal not marked by a band.

8) Assembler:  A software development tool that translates human-

readable assembly language programs into machine-readable code that the target processor can understand and execute.

9) Aperiodic server: A task that responds to events of an application

software

10) Application-specific integrated circuit [ASIC] : A piece of custom-designed hardware in a mass-produced

chip.

11) ARM [Advanced RISC Machine] : A 32-bit RISC processor widely used in low-power embedded

applications.

12) Aperiodic: The term is most often used in the embedded context

when scheduling periodic tasks. The issue of what to do about aperiodic tasks and interrupts inevitably arises in real-world systems. Aperiodic tasks become ready to run on the occurrence of unpredictable events.

13) Assembly language: A human-writable form of a processor's native

instruction set. In its typical form, each line of assembly code represents a single CPU instruction. The human-readable representation of each opcode is called a mnemonic.

14) BASIC Stamp: A tiny single-board computer manufactured by

Parallax based on an 8051, PIC, or other microcontroller. The BASIC Stamp is about the size of a postage stamp (hence the name) and executes a variant of BASIC called PBASIC. Inexpensive, self-contained, and easy to program, they're used in education and simple embedded systems that require little horsepower but rapid delivery.

15) Bidirectional:  Describes a type of device or bus that supports two-

way data transfers. To reduce wiring, connectors, and pin counts, it's common to share data on one bus. Data can move from device A to B or from B to A, though not at the same time.

16) Binary semaphore: A type of semaphore with just two states. Often used to

guarantee mutual exclusion.

17) Breakpoint: A location in a program at which execution is to be

stopped and control of the processor switched to the debugger. Mechanisms for creating and removing breakpoints are provided by most debugging tools.

18) Compiler: A software-development tool that translates high-level

language programs into the machine-language instructions that a particular processor can understand and execute. 

19) Complex instruction set computer [CISC]: Describes the architecture of a processor family. CISC

processors generally feature variable-length instructions and multiple addressing formats and have a small number of general-purpose registers.

Intel's 80x86 family is the quintessential example of CISC.

20) Complex programmable logic device (CPLD): A larger, more capable PLD. Each CPLD typically

consists of several programmable logic blocks plus a matrix of programmable interconnecting paths. CPLDs can be used to create larger and more advanced logic circuits than PLDs.

21) Cross-compiler: A compiler that runs on a different platform from the one for

which it produces object code. Often even the processor architecture/family of the host and target platforms differ.

22) Deadline: In a real-time system, the time at which a particular set of computations or data transfers must be completed. There are typically consequences associated with missing a deadline. If the deadline absolutely, positively must be met every time or else, it is called a hard deadline. Hard deadlines have dire consequences when missed. Other deadlines are said to be soft deadlines.

23) Emulator: Any debugging tool that pretends to be a system resource and

adds additional functionality or remote visibility. 

24) Endianness: The attribute of a hardware or software architecture that

indicates how multibyte values are represented and stored. The two possibilities are called big-endian and little-endian. 

25) Firmware: This term is interchangeable with embedded software and

sometimes is used even when the executable is not stored in ROM.