Hello Mr. Demetris S,
There is a very good freeware program called JSIM51 which
can simulate interrupts. I use it myself for debugging
interrupt service routines and it works great. A web site
is given below where you can download this program.

JSIM51 is an efficient tool for software development
for 8051-Controller and derivatives. The program simulates
the processor core and selected hardware functionality's.

http://home.t-online.de/home/Jens...jsim-g.htm

Good luck,
Regards,
Charles Bannister