Anil,

While your question is more pointed this time, it is still somewhat vague. The thing that you lack is an application; there are many degrees of freedom here:

* Available LED's
- Voltage drop
- Current draw
- Intensity
* 8051 I/O structure
- Source/sink current
- Output voltage
- Supply voltage
* LED driving scheme
- Directly switching the LED?
- Use a transistor?
- Use an IC?
* Other concerns
- Power dissipation
- Ambient conditions

This would make a good interview question because it can show how well you know these areas. Apparently you don't know them very well, so I would suggest you do some homework. This is what I do when I want to learn about what is out there - go to a distributor like Digikey and search through their inventory. Read the datasheets of all the different types of LED's that you don't know about. Learn about the little quirks of LED's in general and the variants in particular. Go to manufacturer websites like Kingbright. You will find many products that you can't get from distributors and you will get familiar with each company's product line.

By the way, it is helpful to have the discussion in the 8052.com forum instead of by email. That way others can learn from the interactions and there will be an archive for others to search through in the future.

- Lee