Thanks for that.

The code i have should work. The problem lies in the chip im using.

The boards we have were based around the 80C51FA, with only 128 ram, and 256k ROM. I was using a pre-writen boot loader, that executed code at address 0x8000.
This workes fine with the old chips. But i have now replaced these (as they are obsolete) with the 89C51RDm with 64K flash and 1k Ram.

The same boot loader doesn;t seem to execute programs in external RAM.

I have come to the conclusion that the address 0x8000 falls in the internal memory space, so will not execute external code at the same address.

But im just guessing here, and not really sure what the problem is.

Any sudjestions appritiated?

Thanks Anand