On Tue, Aug 10, 2004 at 09:45:44PM -0400, Dave Dunfield wrote: 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. RAM is $0000-$7FFF on a 32K PET. Video memory starts at $8000. ROM space starts at $9000 and goes to $FFFF except for a chunk in the $Exxx block that is for I/O chips (6520, 6522...). Note that depending on how your machine is equipped, it is likely that there are a couple of empty ROM blocks at the bottom of ROM space. On a BASIC 4 machine, ISTR $9000 and $A000 were open for user-added firmware (BASICaid, BASIC Toolkit, TMON, WordPro, etc.). Mine were always full. :-) 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. As for a memory map... $0000-$00FF is zero-page... 99% of it is allocated when running BASIC. $0100-$01FF is the stack. $0200-$03FF is used by various things like line edit buffers, cassette buffers, 8032 screen editor variables, etc. BASIC RAM starts at $0400 with a zero byte, then your program goes from $0401 up. At this level of detail, all PETs are the same. What changes from model to model is exactly which zero page locations are used for exactly which functions, etc. Note that unlike the VIC-20 or C-64, you cannot move screen RAM around by twiddling a video chip register... the video is fixed on PETs. -- Ethan Dicks, A-130-S Current South Pole Weather at 11-Aug-2004 01:50 Z South Pole Station PSC 468 Box 400 Temp -65.8 F (-54.3 C) Windchill -106.6 F (-77 C) APO AP 96598 Wind 15.6 kts Grid 348 Barometer 682.5 mb (10532 ft) Ethan.Dicks(a)amanda.spole.gov http://penguincentral.com/penguincentral.html