Text V embedded systems

An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, often with real-time computing constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a general-purpose computer, such as a personal computer, can do many different tasks depending on programming. Embedded systems control many of the common devices in use today.

Since the embedded system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product, or increasing the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.

Physically, embedded systems range from portable devices such as digital watches and MP4 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.

In general. “embedded system” is not an exactly defined term, as manu systems have some element of programmability. For example, Handheld computers share some elements with embedded systems – such as the operating systems and microprocessors which power them – but are not truly embedded systems, because they allow different applications to be loaded and peripherals to be connected.

Debugging. Embedded Debugging may be performed at different levels, depending on the facilities available. From simplest to most sophisticated they can be roughly grouped into the following areas:

Interactive resident debugging, using the simple shell by the embedded operating system (e.g. Forth and Basic).

External debugging using logging or serial port output to trace operation using either a monitor in flash or using a debug server like the Remedy Debugger which even works for heterogeneous multicore systems.

An in-curcuit debugger (ICD), a hardware device that connects to the microprocessor via a JTAG or NEXUS interface. This allows the operating of the microprocessor to be controlled externally, but is typically restricted to specific debugging capabilities in the processor.

Because an embedded system is often composed of a wide variety of elements, the debugging strategy may vary. For instance, debugging a software- (and microprocessor-) centric embedded system is different from debugging an embedded system where most of the processing is performed by peripherals (DSP, FPGA, co-processor).

Контрольные вопросы:

1. What is an embedded system?

2. What kinds of an embedded system are there in use?

3. What is an in-circuit debugger (ICD)?

4. What do you know about the debugging strategy?

Text VI computer networking

Computer networking is the engineering discipline concerned with communication between computer systems or devices. Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called RFCs. Computer networking is sometimes considered a sub-discipline of telecommunications, computer science, information technology and/or computer engineering. Computer networks rely heavily upon the theoretical and practical application of these scientific and engineering disciplines.

A computer network is any set of computers or devices connected to each other with the ability to exchange data. Examples of different networks are:

Local area network (LAN), which is usually a small network constrained to each other covers a large geographic area; wide area network (WAN) that is usually a larger network that covers a large geographic area; wireless LANs and WANs (WLAN & WWAN) are the wireless equivalent of the LAN and WAN).

All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fiber. Power lines and various wireless technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet).

Network administrators see networks from both physical and logical perspectives. The physical perspective involves geographic locations, physical cabling, and the network elements (e.g., routers, bridges and application layer gateways that interconnect the physical media. Logical networks, called, in the TCP/IP architecture, subnets, map onto one or more physical media. For example, a common practice in a campus of buildings is to make a set of LAN cables in each building appear to be a common subnet, using virtual LAN (VLAN) technology.

Informally, the Internet is the set of users, enterprises, and content providers that are interconnected by Internet Service Providers (ISP). From an engineering standpoint, the Internet is the set of subnets, and aggregates of subnets, which share the registered IP address space ans exchange information about the reachability of those IP addresses using the Border Gateway Protocol.

Networking is a complex part of computing that makes up most of the IT Industry. Without networks, almost all communication in the world would cease to happen. It is because of networking that telephones, televisions, the internet, etc. work.

Local area network (LAN)

A local area network is a network that spans a relatively small space and provides services to a small number of people.

A per-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: single-service servers; print server, where the server performs one task such as file server; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers may be connected in many different ways, including Ethernet cables. Wireless networks, or other types or wires such as power lines or phone lines.