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80186 Microprocessors: Introduction and Architecture

Hello friends, today we are going to discuss the 80186 microprocessor with integrated peripherals. The Intel 80186 is an improved version of the 8086 microprocessor. 80186 is a 16-bit microprocessor with a 16-bit data bus and a 20-bit address bus. It has a programmable peripheral device integrated into the same package. The instruction set of the 80186 is a superset of the instruction set of the 8086. The term super-set means that all of the 8086 instructions will execute properly on an 80186, but the 80186 has a few additional instructions. The following figure shows the block diagram and pin diagram of 80186. The CPU is divided into seven independent functional parts. 80186 internal block diagram  80186 68-pins pin diagram  Functional parts of 80186 Microprocessor The Bus Interface Unit (BIU) Execution Unit (EU) Clock Generator Programmable interrupt controller Programmable Chip Select Unit (CSU) Programmable DMA Unit Programmable counter/timers The Bus Interface Unit ...
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Classification of Computer Networks

Hello friends, today we are going to discuss the brief classification of computer networks. These are categorised in two types.
1. Based on transmission mode 2.  Based on network scale 

Based on transmission mode:

There are two types of
 transmission technology

– Broadcast networks:

Broadcast networks have a single communication channel that is shared by all computers in the network.

Short messages, called packets are sent by any machine and received by all other computers on the network
An address field within the packet is used in the message to select the target machine.
Upon receiving a packet, a computer checks the address field. If the packet is intended for itself, it processes the packet; if the packet is intended for some other machine, it is just ignored.
Broadcast systems also allow the addressing of a packet to all destinations by using a special code in the address field. When a packet with this code is transmitted, it is received and processed by every machine on the network. This mode of operation is called broadcasting.
Some broadcast systems also support transmission to a subset of the machines called multi-casting.
Smaller, geographically localised networks tend to use broadcasting.

– Point-to-point-networks:

This network consists of many connections between individual pairs of machines.
A message packet may have to visit one or more intermediate machines before reaching its intended target.
Multiple routes, of different lengths, are possible, so routing algorithms play an important role.
Most large area networks are point-to-point networks.

• Based on network scale:

Local area networks (LANs):

LANs are privately owned networks within a single room, building, or campus of up to a few kilometers in size.
LANs are restricted in size, often use a transmission technology consisting of a single cable to which all the machines are attached.
Various topologies are possible for broadcast LANs as shown in the figure, a bus (Ethernet) or ring topology (Token Ring).
At any instant, only one machine can transmit successfully (unless switches are used to segment the network).
The arbitration mechanism may be centralized or distributed. IEEE 802.3 is called Ethernet.
It operates at 10 Mbps (Ethernet), 100 Mbps (Fast Ethernet), and 1000 Mbps (Gigabit Ethernet).
In a ring, each bit propagates around on its own, not waiting for the rest of the packet to which it belongs.
IEEE802.5 (the IBM token ring), is a popular ring - based LAN operating at 4 and 16 Mbps.
Two broadcast networks a. Bus b. Ring
Two broadcast networks a. Bus b. Ring


Metropolitan area networks (MANS):

A MAN is basically a bigger version of a LAN and normally uses similar technology.
It covers corporate offices or a city and might be either private or public.
A MAN can support both data and voice with local cable television networks
A MAN has also a special category standard called DQDB (Distributed Queue Dual Bus) or for people who prefer numbers to letters, IEEE 802.6.
DQDB consists of two unidirectional buses to which all the computers are connected, as shown fig.
Each bus has a head-end, a device that initiates transmission activity.
Traffic destined to the right of the computer uses the upper bus while traffic destined to the left uses the lower bus.
The architecture of the DQDB MAN
The architecture of the DQDB MAN

Wide area networks (WANs):

WAN covers a large geographical area, mostly a country or continent.
It consists of collections of machines called hosts (or also called end systems) intended to run applications.
The hosts and their LANS are connected by a communication subnet that carries messages from host to host.
In WANs, the subnets consist of two distinct components: Transmission lines and switching elements.
Transmission lines also called circuits, channels, or trunks, move bits between machines.
The switching elements are specialized computers used to connect two or more transmission lines. When data arrive on an incoming line, the switching element must choose an outgoing line to forward them on. These switching computers are called routers. (Packet switching nodes, intermediate systems, and data switching exchanges)
Relation between hosts and the subnet
Relation between hosts and the subnet

Each host is generally connected to a LAN, on which a router is present. The collection of communication lines and routers (but not the hosts) form the subnet.
When a packet is sent from one router to another via intermediate routers, the packet is received at each intermediate router, stored there until the required output line is free, and then forwarded. A subnet using this principle is called usually packet-switched (point-to-point, store, and forward) subnet
When a point-to-point subnet is used, the router interconnection topology is an important issue in WAN design. The figure shows several possible topologies.
Some possible Topologies
Some possible Topologies

Fig. some possible topologies for a point-to-point subnet. (a) Star, (b) Ring,
(c) Tree, (d) Complete, (e) Intersecting rings, (f) Irregular.

Internetworks (Internet):

A collection of interconnected networks is called an internetwork or just the internet.
Sometimes by using machines called gateways to make the connection and provide the necessary translation between the different hardware and software components of the internetwork.
A common form of internet is a collection of LANs connected by a WAN.

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Comments

  1. opennaukri9/04/2021

    Thanks for suggesting good list. I appreciate your work this is really helpful for everyone. Get more information at Output And Input Devices Of Computer. Keep posting such useful information.

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