Re: Series 80 Programmable ROM module clone - update Message #4 Posted by Olivier De Smet on 1 Dec 2004, 5:05 a.m., in response to message #3 by john
I think the limit is that you can only use 1 ROM module (written somewhere in the manual I think) due to electrical decoding of lines over the bus.
You can then add 2 roms with a Programmable rom module.
You can have 5 included roms in an HP86B.
So a max of 13 roms and a software limit of 15 or 16 (have to look at the system sources).
In fact the REAL HARD part is the connection of this module to the specific HP8x bus. Then you need to decode the IO adress to select the current rom. After that, the number of rom allowed is just a eeprom capacity limit (and a software one).
Perhaps creating a new ROM expansion module could be easier that mapping the rom module pins.
André Koppel has some nice pdf for a 'system' view of the HP 8x series.
Olivier
|