Hello Mr. Waqar Zaka,

Keep it simple, make it fun (KISMIF) should be the guiding light in your quest to learn more about assembly programming.

Some the most brilliant men [1] in history didn't understand the technical stuff of what they were doing but yet they succeeded.

There are multitudes of examples of what you what to do at your fingertips. All it takes is just piecing them together to build your clock. It will automatically update BCD memory variables which are a piece of cake to interface to a seven segment display.

The same program with a little bit a work could be used to make a start/stop timer.

There is already an assembly program written to perform a real time clock available at the following web site. http://members.aol.com/cpu8052/modem1.html.

Interfacing common anode seven segments readouts is also a piece of cake. I have used 74LS47 and 74LS138 to interface up to eight of them. I will try to get a schematic and printed circuit board on the net in the near future for you to look at.

Good luck,

Regards,

Charles Bannister

[1]
Samuel Morse (invented morse code)
Lear (invented eight track tape player, lear jet)