Von Numann & Harvard Memory Architecture

Von Neumann

           

                In the von Neumann architecture CPU can either read an instruction or read/write data from/to the memory. Both of these operations cannot occur simultaneously as the data and instructions use the same system bus. This means that it is necessary to fetch instruction and data from the same memory space, which limits bandwidth because it can only transmit one piece of data or one instruction at a time.

 Harvard Architecture

The most obvious characteristic of the Harvard Architecture is that it has two different data buses to. The contacts are CPU to RAM and CPU to ROM.  Using these buses it is possible to access program memory and data memory simultaneously. Typically, code (or program) memory is read-only and data memory is read-write. A Harvard architecture microcontroller can thus be faster for a given circuit complexity because instruction fetches and data access do not contend for a single memory pathway. Compare to von numann architecture Harvard Architecture can achieve higher clock speeds; caches are useful as the memory speed is proportionally slower. Harvard architectures tend to be targeted at higher performance systems, and so caches are nearly always used in such systems. Harvard Micro processors can be much faster than a von Neumann Micro processor because data and program do not contend for the same information pathway, and storing the program in an immutable read-only memory can result in vast reliability improvements.

           Thank you everybody, if you are struggling with any of this information, please post a comment. Comments are welcome.

How to configure your ADSL router

Hi, this article only helps for the people who are in Sri Lanka and having ADSL Home Packagers. This explains step by step how to configure D link ADSL router.

To configure the router, first you should have to log in to your ADSL router. To do that properly you should follow following steps.

Step 1

Connect the PC to the router using Ethernet cable.

Open the web browser and enter the address http:// 192.168.1.1

Then default user name is “admin” and password is “admin”.

Then you will appear a web page that included router configurations.

When you connect your PC to the ADSL router using network cable (With RJ45 connectors), will see POWER, STATUS and LAN indicators are properly working. And also you can use any browser according to your flavor.

Step 2

In D-link menu you have to go for “Advanced setup”.

Then you have to enter values for PORT ,VPI and VCI.

PORT - 0

VPI - 8

VCI - 35

Then select “Service Category” as “UBR without PCR”.

“Connection type” as “PPP over Ethernet (PPPoE)”.

Then need to select “Encapsulation Mode” as “LLC/ SNAP-BRIDGING”

And enter the “user name” and “password”.

Above user name and password is supplied by your ISP (Internet Service Provider).

Step 3

After entering those instruction need save those configuration and reboot the router.

Step 4

Can see DSL and Internet indicators are blinking on the router.

How obtain configuration data

Call 1243 number using SLT telephone and follow instruction to connect with customer care and ask them.

Then following information will provide.

Required data from ISP (Sri lanka Telecom)

VPI - 8

VCI - 35

Connection type as “PPP over Ethernet (PPPoE)”

Encapsulation Mode as “LLC/ SNAP-BRIDGING”

Thank you everybody, if you are struggling with any of this information, please post a comment. Comments are welcome.

Customer Premises Equipment

          Hi, this article provides you to have knowledge about some telephone equipments located in your home. Basically we called them as Customer Premises Equipments (CPE). When telephone operator provides the telephone facility to a particular place, these equipments are installed by them.

           The following figure gives an idea of that how they arrange in order.

Customer Premises Equipment

            The telephone connection line is coming from out side of the building. First it comes to dis-charger unit. This unit responsible for protecting telephone from high voltages that are coming from out side. Especially local home telephones are collapse from lighting. Therefore there is an special mechanism to ground that incoming high voltage. There is an external wire comes out from dis-charger and it goes to earth. And also it is build with very simple circuit. 

Rosette Box

           After the dis-charger unit this telephone wire comes to a device call Rosette Box. It is consist of only cross connection. It has two interfaces and they are normal telephone wire connection and RJ11 interface. This device is used for have the line with RJ11 connectors.

           Now the wire has RJ11 connectors at both sides, therefore it is easy to do the wiring. The wire between Rosette box and splitter is called Rosette code. Rosette code is a code which has RJ11 in both sides. Then the wire connects to the Telephone through a splitter. Splitter is used to separate voice frequency and ADSL frequency. The splitter is consisting with low and high pass filters. Low pass filter is used to filter-out the lower frequency of incoming signal and high pass filter is used to filter-out high frequency.The ADSL line then connects to modem and after goes to computer. Yes, not only a modem we can use ADSL router to do that job.

        Next case is little bit different than previous, but you can see the same equipment arrangement is there.  In that application that house has 2 bed rooms and a living room. Now we are going to setup the Internet connection and normal telephone connection. The customer needs ADSL connection to his 4 desktop computers and to a Laptop. And also he would want to use a cordless phone is used in one of his bed room. Following figure will express better idea of customer premises equipments.

Customer Premises Equipment

          Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you.