11 Aug
2004
11 Aug
'04
12:04 a.m.
Thanks for the very useful information!
If you want the keyboard to work, you'll need to
set up one of the 6520s. If
you just want to see stuff on the screen, there's a table in the ROMs that is
loaded into the 6545 CTRC. There are two sets of values, one for 4032 and one
for 8032 (different ROMs). The other chips are used for IEEE-488, cassette
control, and the user port. No initialization for your purposes required AFAIK.
I checked the funet archive and found some details, however the PET "IO"
document
describes only the 6520's and 6522 - there is no mention of the video controller.
The only other references I found to I/O addresses were obviously a disassembley,
with such meaningful labels as:
AE810 DS 1
AE811 DS 1
AE812 DS 1
Can you tell me where (address) the 6545 is located?
I'm going to begin disassembling the Kernel ROM and see if I can figure out enough
to turn on the screen - don't need keyboard (yet) - just want to be able to display
some info.
Once you extract the table and load the 6545, you
should be able to sling
bytes at the screen starting at $8000. Remember that "POKE codes" are not
ASCII nor PETSCII, they are character codes from the chargen ROM (not
accessible to 6502 memory space). There should be some docs on this on funet.
As an example, though, while you might "PRINT CHR$(65)" to get an 'A' on
the
screen, you'd "POKE 32768,1" to get that 'A' to appear in the upper
left
corner of the screen.
I didn't see an obvious reference - can you give me a pointer - all I really
need right now is 0-9,A-F and SPACE - I can determine these by fooling with
the working machine if I have to.
Btw, do anyone have (or know of) a working stand-alone monitor program which
can be stuffed into the Kernel ROM position?
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Vintage computing equipment collector.
http://www.parse.com/~ddunfield/museum/index.html