Hi Amarnath,

The P89C51RD2BN is a second generation product in this group and allows for user programmable clock rates ( 6 or 12 ).

Otherwise there does not seem to be any other quirk and the BN mostly has got something to do with the package & temperature combinations. HAve a look at the model codes in the data sheet from this link :
http://www.semiconductors.philips.com/pip/P89C5...#datasheet

I dont think there is any problem with the chip per se. But you may have major problems with WINISP. Try downloading FlashMangic from www.esacademy.com and all your woes will be a thing of the past.

Raghu