NV RAM update

[jsg at donet.com]

Hi all,

I was able to get the Dallas battery backed-up RAM chip working in the
730 over the weekend. I can now read/write bytes and execute code
from the address space usually containing the EPROM. The address space 
is switchable between NVRAM and EPROM (soon to be FLASH). There is
also a write protection switch to protect the NVRAM contains in case of 
a "crash".

The next task is to write aldl routines to modify data on the fly. 

john gwynne