I replaced Phillips P80C51FA-4A with Atmel AT89C51RD2-SLSUM as the phillips one is obsolete. The specification of the micrprocessor seems to be same. Any general idea of why it won't work?

 

They are most unlikely to use the same instruction set or register addresses so I wouldn't expect it to work.

 

Any general idea of why it won't work?

Lots of them. Why do you think it *will* work?

 

Did you program the Atmel part before testing it? Just asking.

 

Thank You to all for response. Yes, I did program the same way I used to do it for Phillips. But doesn't work. I thought it will work because of the almost same specification. I am not sure where i am going wrong comparing the specification. Also is there any part similar to phillips which I can try and replace?

 

They are most unlikely to use the same instruction set or register addresses so I wouldn't expect it to work.

According to the part numbers I can confidently tell you that the register set and the instruction set they are the same. The problem is probably in the implemented peripherals. My advice is to start the investigation by starting with a simpler program. Get that to work and then build out your knowledge base on how the two parts are different.

 

I think the programming method is different. The old Philips part uses OTP memory which I suspect is EEPROM while the Atmel part uses flash and the programming protocols are different. You will need to use a programmer designed for the ATMEL part.

I understand that the 89C series parts can be programmed with FLIP, but you need to check for yourself.
http://www.atmel.com/tools/flip.aspx

Following Papabravo's suggestion, it would be very helpful if you have the source code for the Philips chip.

 

I thought of the programming would be different for Atmel but when I see the data sheet of both (links attached below) I noticed that both are using EEPROM which made me believe that Atmel would work.

http://www.atmel.com/Images/doc4235.pdf

http://htmldatasheet.com/philips/p80c51fa4a[1].htm

 

The Philips part used EPROM for program memory but the Atmel part uses EEPROM for long term data storage and uses flash for program storage.

 

Yes, Now I get it.

 

Yes, Now I get it.

You can succeed at this project if you take things one step at a time, just like peeling an onion.