Looks like somebody asked something and went on a holiday !! Ritesh - is the problem still bugging or has been solved ?

The code looks fine. But then why a 'call' when you can directly 'vector' ? Also 'mov sp, #30H' can be ' mov sp, #80H ' and you can almost forget about stack overflows besides getting the full direct RAM for use - that is if you use an MCU with 256 bytes of RAM. And I do suppose your source of interrupt conforms to the required minimum timing as specified in the DS.

Also I am not sure what speed the clock is - if it is something like 12Mhz, then your delays are just too small for any human perception.

I am happy that lots of alternative MCU's have been suggested. However the problem in getting one of those is the issue of sourcing. This can vary from " Just not available here" to " You cannot change the MCU type "

Raghu