|NoV-64 is ready! :-) Preliminary info.|
Message #1 Posted by Diego Diaz on 21 Sept 2008, 6:12 p.m.
Finally, NoV-64 is fully operative.
- 48K (12pages) Flash ROM distributed as follows:
... 4 pages (block 0) holding Advanced HEPAX emulation.
... 4 pages (block 1) to load primary user selected ROM images.
... 4 pages (block 2) to load secondary user selected ROM images.
Block 0 is always active providing HEPAX functionality.
Block 1 is active by default when the module is plugged. (uses ports 1 or 2)
Block 2 can be swaped with Block 1 by means of control word at address H'4100 (explained below)
Allowed pages for ROM blocks are #C to #F
Also both blocks can be disabled by means of such control word.
- 64K (16 pages) non volatile RAM.
... 4 blocks of 4 pages each, addressed to pages #8 to #B, can be used as HEPAX RAM or to hold ROM images the way Advanced HEPAX does.
Active RAM block is also selected by means of control word at H'4100. There always be an active RAM block.
Control word usage:
HEXEDIT command allows direct access to any memory position.
Enter: 4100 at the [ADR: _ _ _ _ ] prompt.
You'll see [4100 100 _ _ _ ]
Bits meaning of control word:
b9: 1=ROM block 2 enabled, 0=ROM block 2 disabled.
b8: 1=ROM block 1 enabled, 0=ROM block 1 disabled.
b7-b2: Not used.
b1-b0: 00=RAM block 0 enabled, 01=RAM block 1 enabled, 10=RAM block 2 enabled, 11=... mmm, sure you can guess that one... :-)
Example 1: To enable ROM block 2 and select RAM block 3, write 203 into H'4100, then turn your HP-41 OFF and ON again.
Example 2: To Disable both ROM blocks and select RAM block 0, write 000 into H'4100, then turn your HP-41 OFF and ON again.
ROM block 1 has precedence over block 2. In case bits 9 & 8 were both set to 1 bit 9 will be erased leaving only ROM block 1 enabled.
Clearing bits 9 & 8 will disable both ROM block allowing the use of ports 3 and 4 to plug physical ROM modules in.
Changing the RAM block will be effective inmediately. To swap or disable ROM blocks power cycling the HP-41 is obviously needed.
It'll still take a few days to update my web page with fully detailed info, and include NoV-64 into the new Windows Configuration Utility, however any comments, questions and/or suggestions will be welcome.
Best wishes from the Canary Islands in this last Summer day.