PET startup sequence?? (was LF: Commodore PET schematics,troubleshooting info)

From: Dave Dunfield <>
Date: Wed Aug 11 07:04:28 2004

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?

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Vintage computing equipment collector.
Received on Wed Aug 11 2004 - 07:04:28 BST

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