brfennpocock

Personally, I use 64tass, but I came up on the Commodore 64.

I'd bet on the ROM being bad … Those are usually (always?) socketed ROM chips, so you could try reading it into an EPROM burner (assuming you have access to one) to verify its contents vs. one of the various on-line sources of ROM images …

If I understand the problem correctly … PETSCII isn't used for screen display codes; I believe the PET will use a similar (same?) code set as the VIC-20 / C=64 / C=128, seen in http://sta.c64.org/cbm64scr.html — It's like PETSCII with the 3° group of 32 chars swapped into the 1° position. A in PETSCII = $41, A in screen codes = $01. A reverse char is the same as its normal char & $80 (+128), so where A is $01, reverse A is $81; π is $5e, reverse π is $de. To get the PETSCII for a non-reverse char, and/or a flag to indicate if a char is reversed, REM screen address AD% = (screen code base RAM address) + Y% * (screen width) + X% REM is it reversed? 0 = false, 128 = true. RV% = PEEK(AD%) AND 128 REM convert screen code to PETSCII SC% = PEEK(AD%) AND 127 PC% = SC%:IF SC% < 32 THEN PC%=SC%+64

Personally, I'd do something like MODE_Random_Play = 1 MODE_Not_Random = 2 .if GAME_MODE = MODE_Random_Play jsr SubGetRand .else lda SWCHA .endif disclaimer: I don't use dasm, so YMMV

Just a guess, but it looks like a splitter for Datasette recorders … connecting two up to one computer so you could read one and write the other … probably for fast* copying (* where “fast” means 300 Baud)

There's a scan at ftp://www.zimmers.net/pub/cbm/manuals/drives/1581_Users_Guide.pdf

Do I correctly understand that you're interested in writing (also) a PLATO terminal for the ’64 or ’128? I'm curious if a limited-capability terminal on a ’64 would really be usable for playing most of the games on PLATO … ? but seems like you're definitely more the expert than I … In particular: remapping from ( 512 × 512 px = 64 × 32 ch ) to ( 320 × 200 px = 40 × 25 ch ) or ( 640 × 200 px = 80 × 25 ch ) in a non-disruptive way. It looks like, per your text file, the A][ version centered a 192×256px screen and expects its own special 4×6px custom character sets? That would certainly work “passably” on a VIC-II, as long as the 4×6 fonts exist — and with some weird color artefacts across 8×8px cell boundaries, of course. On the other hand, it seems like the VDC on the ’128 should handle 512×512 @ 16×8 just fine — definitely as 640×512, with margins blanked on each row, although it wouldn't surprise me if some fudging with the VDC registers wouldn't allow for directly mapping exactly 512×512, albeit with not-precisely-square pixels. I've played around a bit with (including submitting the odd patch to) Linux PTerm, I'd be interested in lending a hand if possible.

Strangely, I couldn't find anywhere to buy the (standard .1" 12/24 pin) edge connectors for the 2600, so I had these printed up by (wonderful) OSH Park … just posting here in case anyone else might have a use for them. https://oshpark.com/shared_projects/nNu0ppnR I personally just soldered pin strips to the 24 solder points and used female-to-male breadboard wires to break it out, but do whatever you like. The +5V and GND pins are duplicated to be a little easier to alligator-clip them, if you prefer. Unfortunately there's a minimum order of 3 (Came out to about $18 for me), but … maybe someone else will have a use for this. (And, no, I don't get a kickback from OSH Park, you're welcome to the KiCad or Gerber files if you want them.) Speaking of which, I do have a spare one (I used 2) if anybody wants it.