But, Raghu, the P89V51RD2's bootloader can be "talked to" he same way as the P89C51RD2's... You are using intelhex-style "commands" in both cases, and most of them are the same. Maybe the biggest difference is the method of entering the bootloader - but with the "V" it is maybe even easier than with the "C" - in the terminal program, you switch on CAPS LOCK, then simply press and hold "U" to start "autorepeating" it; and reset the controller.
To upload the code itself from an intelhex file, you need to set some reasonable end-of-line delay, as the terminal program is not aware of the "." sent by the bootloader upon succesful programming of a line. I usually use 200ms, although based on datasheets' value for programming a byte and line length, often less would be enough. I usually aso use 9600 or 19200 bauds to remain on the safe side. Although this all results in longer than optimal programming times, for ocassional field usage when other tools failed, as a last resort, it would suffice.
A small trick, it is good to carry around a couple of small files containing a single "intelhex" line with often used commands, e.g. erase.hex, password.hex...

Jan Waclawek