> From: Joshua Woods <j.woods@qut.edu.au>
>
> Hello,
>
>         I am working on  a design, using a PIC16C74.
>
>   I need 128Kbytes of Non-Volatilie storage, and 64Kbytes of Program
> storage.
>
> Can you suggest some options. I may have to use serial EEPROM for the
> 128Kbytes of storage, however I think serial EEPROM will be to slow for
> Program storage.
>
> My plan was to use the 4K of EPROM on the OTP version of the PIC to
> execute code on the external FLASH or EEPROM?
>
> Is it possible to address all this memory using parallel devices?

The 16C74 has 3 full 8-bit ports (B,C,D), plus a 3-bit (E) and a 6-bit (A).
Assign D as your data port (8-bits wide).  B and C form the address of
a byte in a 64K page, then E0 and E1 allow for a total of 256K.  E2 can
be used as a write enable.  The 'unused' combination of E0=1, E1=1
(since you only need 192K) is used to tristate the memory so that you
can turn D into an output for a subsequent write cycle.

This leaves all of A for I/O.

Of course you have your work cut out for you implementing a good interpreter
in the PIC's program memory.  Basically, you are microcoding...

Regards,
SJH
Canberra, Australia