The CY8C28433 is in every respect the larger chip (SRam, IO-Blocks etc), so your firmware will at least fit into.
None the less you will need the firmware's source code and project data to clone the project from the old chip into the new. That is a job usually done within 10 minutes if you know how. I doubt that it will be possible to directly program the old firmware as a hex-file into the 28433 and have all functions working.
Thanks for your speedy reply Bob.
I thought it would take a while for a response so i did program the CY8C28433 with the hex file made for the CY8C27443. It programmed just fine, all functions worked just fine except eprom related functions. Any suggestions?
It may be that your flash security file needs editing to call out the right blocks the new device
Also for both versions print out datasheet for the new and old project and compare settings.
Some global settings, present in one release do not appear in another (Cypress is slowly
working on that issue) may need to be "fixed" up.
while the new chip may seems to work fine. I would recompile the code. Some times it would take a long time for the bug to show up.