Denial

I guess you are asking this because you want to know how to dimension the screen buffer for your own emulator, right? Yes for the emulator at the moment but I'm also thinking about a VIC chip replacement for those 3 dead machines of mine. I still have the option of fiddling with an FPGA so just try...

I bet this is a question for Mike. :-) What is the maximum number of pixels the Vic chip can display on a TV screen - this is including moving the screen from top-leftmost to bottom-rightmost? In other words, if you had to a design a monitor that would handle the Vic's max screen size in any x/y pos...

I spoke too soon! I can't get '2' to work. I can see that the matrix scan is definitely working - it stores $38 (56) in $cb as expected.. but for some reason number 2 doesn't appear on the screen. All the other letters and numbers work. Would this have something do with 2 having the double quote sym...

This has been bugging me for a while. I had the below book when I was a kid: https://i.imgur.com/RHiMzb9.png I would have thought I'd be able to find a PDF of it bask in some nostalgia but I can't find it anywhere. It isn't on the DLH Bombjack site or archive.org Does anybody have a .pdf they would ...

Well.. I had the wrong value written to my matrix (typo!) so that's why some keypresses wouldn't work. The amount of diassembly debug was also slowing things down that I was missing the key up event.. so I think I have this mostly working now :-) I haven't implemented colour on the screen yet but th...

I don't understand what this bit of code is doing: LAB_EB1E LDA #$00 ; clear A STA LAB_028D ; clear keyboard shift/control/c= flag LDY #$40 ; set no key STY LAB_CB ; save which key STA LAB_9120 ; clear VIA 2 DRB, keyboard column ### HERE LDX LAB_9121 ; get VIA 2 DRA, keyboard row ### HERE CPX #$FF ;...

Pressing a key causes the row/column combination to shorted. The 6522 pulls inputs high when unconnected so this results in the value 11110111 being returned for column 4. I've tried reversing my bit orders for both column and row. I now return F7 for 'M' but nothing appearing on the screen still. ...

After reading a few more posts, I thought perhaps I should be returning 0 for keys that are pressed down rather than 1.. So now I'm returning $ef for M in $9121.. but still no keypresses being detected by the VIC.

I must be missing something else?

Ultimately, the easiest way to get keyboard input correct will be to mimic the keyboard matrix and VIA registers, and let the KERNAL do all the decoding work. Otherwise you'll get stuck in all sorts of definitions by cases. Hmmm. I've logged all of the writes to $9120. I'm returning $10 for 'M' whe...

Ultimately, the easiest way to get keyboard input correct will be to mimic the keyboard matrix and VIA registers, and let the KERNAL do all the decoding work. Otherwise you'll get stuck in all sorts of definitions by cases. That is starting to sound like the safest option. I wonder where the best p...

I guess your emulator should take care of the via registers (the keyboard matrix) and let the kernal interrupt do the updates of these registers you are talking about. I guess otherwise you are rewriting the rom or designing your own system. In this case, I guess you should compute the correct asci...

What is put into the keyboard buffer by the KERNAL is already the fully decoded result after the modifier keys have been read and the corresponding decoding table has been chosen. That makes sense Mike. Cursor Left and Cursor Up I have already got working - and that is really Cursor Right and Curso...

I've made a rubbish Vic emulator (I have my reasons :-) ) .. I've managed to intercept keys on Windows and place them into the Vic's keyboard buffer at $277 and by setting $c6 to 1 (for 1 keypress). That works great - I can get most keys to work. The problem I'm having is trying to understand how Ct...

srowe wrote: ↑Thu Oct 05, 2023 1:21 am That's precisely what the carry bit is for, so your original code should have been

Sigh.. Of course! Why didn't I see that? Thanks. I'll make a note for next time.

I think I was going about this the wrong way anyway. I've changed my code - now I'm checking for SRC_PTR_LO and DST_PTR_LO becoming zero instead. I'm using LDA (SRC_PTR_LO,y) but just keeping Y as zero the whole time and incrementing SRC_PTR_LO each time instead of using ADC and y as the counter.. I...