Sunday, December 31, 2006

Watch Dog Timers

A watchdog timer is a piece of hardware that can be used to automatically detect software anomalies and reset the processor if any occur. Generally speaking, a watchdog timer is based on a counter that counts down from some initial value to zero.

The embedded software selects the counter's initial value and periodically restarts it. If the counter ever reaches zero before the software restarts it, the software is presumed to be malfunctioning and the processor's reset signal is asserted. The processor (and the software it's running) will be restarted as if a human operator had cycled the power.

Introduction to watch dog timers
DS1232 WDT datasheet
(link updated 050107)

AT Keyboard

The AT keyboard was a keyboard with 84 keys introduced with the IBM PC/AT computer. It succeeded the 83-key PC/XT keyboard and therefore did not have many of the features seen on modern keyboards such as arrow keys and dual ctrl and alt keys.

It was later replaced with the 101-key Enhanced keyboard. Nonetheless, "AT keyboard" remains a popular name for any keyboard that uses the 5-pin DIN connector. Many Enhanced keyboards used this, though it was eventually superseded by the PS/2 connector and many modern computers use Universal Serial Bus (USB) connectors instead.

Interfacing the AT Keyboard

Keyboard Scan Codes

IBM PC Parallel Port

Interfacing the Parallel port : An excellent tutorial by Craig Peacock

How stuff works on Parallel Ports

Thursday, December 28, 2006

ASCII codes

ASCII stands for American Standard Code for Information Interchange. Computers can only understand numbers, so an ASCII code is the numerical representation of a character such as 'a' or '@' or an action of some sort.


BCD to ASCII conversion

The HEX equivalent of ASCII '0'(zero) is 30H.Thus to convert a packed BCD to ASCII we need to add 30H to the unpacked BCD

Packed BCD
0011 0100
Unpacked BCD
03H & 04H
0000 0011 0000 0100
33H & 34 H
0011 0011 0011 0100

Monday, December 18, 2006

I2C Bus events

I2C Bus events - a two page handout on I2C bus events

Build and load process for embedded application programs

The following two page handout is about the build and load process for embedded application programs V/s desktop application programs'

Saturday, November 11, 2006

8255 Programmable Peripheral Interface

8255 Programmable Peripheral Interface - Tutorial

8255 Programmable Peripheral Interface - Datasheet (download location 1)

Stepper Motor Basics

Stepper Motor Basics (download location 1)
Stepper Motor Basics (download location 2)

Check out this Wiki article on Stepper motors

Sunday, November 05, 2006

4N25: 6-Pin DIP Package Phototransistor Output Optocoupler

4N25: 6-Pin DIP Package Phototransistor Output Optocoupler

download problems?

In case of difficulty in downloading any files on the blog,you can download it from the email id, I have posted copy of the files there.

I2C Bus Specification

I2C Bus Specification

Check out the blog archives for previous posts

If you are not able to locate previous posts do check out the Archives section

DMX 512 interface

The U.S.Institute of Theatre Technology (hence refered to as USITT) first developed the DMX512 protocol in 1986 as a standard interface between dimmers and consoles. It was a simple concept and was easily adoptable by all concerned. Since the first standard, some improvements was made in 1990 to accomodate some problems and it is now known as the USITT DMX512 (1990) standard.

check out this link to know more about DMX512 interface

MOC3020-M:6-Pin DIP 400V Random Phase Triac Driver Output Optocoupler

MOC3020-M:6-Pin DIP 400V Random Phase Triac Driver Output Optocoupler

An introduction to 8051 development tools

An introduction to 8051 development tools

Safety precautions for development tool:TRIAC + Microcontroller

Safety precautions for development tool:TRIAC + Microcontroller

Saturday, October 14, 2006

Where The Mind is Without Fear

Where The Mind is Without Fear

    WHERE the mind is without fear and the head is held high
    Where knowledge is free
    Where the world has not been broken up into fragments
    By narrow domestic walls
    Where words come out from the depth of truth
    Where tireless striving stretches its arms towards perfection
    Where the clear stream of reason has not lost its way
    Into the dreary desert sand of dead habit
    Where the mind is led forward by thee
    Into ever-widening thought and action
    Into that heaven of freedom, my Father, let my country awake.

    Rabindranath Tagore

Sunday, September 24, 2006

Build Your Own Microcontroller Projects

Check out this site for some cool project ideas based on 8051 family.The site features a lowcost 89c51/89c2051 programmer with the flash programming software(easydownloader)
Build Your Own Microcontroller Projects

Intel Hex file format

Check out his link for a quick idea about Intel Hex file format.
Intel Hex file format

Help required?

In case of any difficulty in downloading the files provided on the blog ,you can find the copy of it in the email id (access only to S7ECE, GEC Idukki Students)

Flash Programming methods

This handout provides an overview of In System Programming of 89C51RDx2 devices. Do read this handout to better understand the 89c51 based trainer kit operation.
Flash Programming methods

Saturday, September 09, 2006

Sorting algorithm animation

Sorting algorithms:
We all know that Quicksort is one of the fastest algorithms for sorting. It's not often, however, that we get a chance to see exactly how fast Quicksort really is. The following link will lead you to applets chart the progress of several common sorting algorithms namely Bubblesort , Insertionsort , Quicksort and Select sort

sorting algorithm animation

80C51 instruction set

80C51 instruction set

Friday, September 08, 2006

8051 development tools

This handout provides an overview about assemblers and 8051 development tools (RIDE and Keil Uvision)
8051 development tools

Sunday, August 20, 2006

Topics for test 3

test date:24/08/06, Thursday

8085 programming model- ie. the programmable registers in 8085
8085,8051 addressing modes:definition,egs
RAM memory space allocation in 8051,
Register bank select:PSW.4,PSW.5 bits
Stacks in 8085 and 8051 - PUSH and POP instruction
How does an 8085 based single board micrcocomputer(ie is a microprocessor trainer kit) work? - read the section from Ramesh S.Goankar's text (Section 3.6) and appendix B

Topics for test 2

test date:22/08/06,Tuesday

Memory map
memory address decoding using NAND gates, Decoders
Tristate Devices
comparison b/w microprocessor & microcontroller
instruction cycle,machine cycle,T-state
Timing diagram of Memory read, opcode fetch,
control signals: RD-,WR-,IO/M-,ALE,EA-,RST,PSEN-

Monday, August 14, 2006

89C2051 datasheet

89C2051 datasheet


This blog intends to serve as a online resource for the paper Microcontroller Based System Design