can u suggest some way to increase the no i/o ports ....i mean any alternative to 8255.......

I shall answer this although you direct the question to 'micro'.

1) use a P89C66x of P89C51Rx2 in both cases you free up all I/O? pins due to the large internal Flash and RAM
2) use a 100 pin Cygnal chip, plenty of I/O. (other manufacturers have high pin count chips as well)
3) use a CPLD, in addition to as many I/O as you can desire you can integrate the ALE latch and the address decoding. (the suppliers such as lattice has free programming software)
4) gang two '51s, one for the high frequency stuff and one for the low frequency fast interrupt response required stuff.

I have used all the above many times, the choice depending on design requirements. As a matter of fact I have one of each on my desk right now.

other choices
PSD chips from ST micro. They are "8255 designed for the '51"
Discrete logic (you can do a lot with a latch)

I have used those in the past.

Erik