Thanks a lot Linas, for your interest. I have got my internet recharge an hour back and writing a reply. I have attached a zipped file of the project here. I wanted to check the project by programming the kit. But I kept the kit in my college. On Monday I'll check it. If this is a wrong file I'll let you know. The program takes a step profile given in the array tempdiff, applies PID scales tempdiff in the range 0 to FE. tempdiff=0 is scaled to 7F. In i2c debugger / the bridge control panel this value will be observed. The temperature control in all cases I studied was too fast. If in any case it gets slow the constant kpdi can be increased till oscillation starts. If 3 consecutive control vectors are of opposite sign it is considered as oscillation. In this program a delay is introduced deliberately to check the data in different  iterations. To check the speed this delay should be removed. If you have any difficulty please let me know.