Denial

Thanks for the explanation, I think I'm starting to get this

I have a quick question about setting up custom characters in assembly, when setting them up do I have to set pointers in order to protect BASIC at all, like when doing this in BASIC, I figure since I'm writing in all assembly and only using a BASIC load I'm safe and don't need to do this. This ques...

I'm going to try this as well as I'm still trying to wrap my head around 6502 assembly and need to understand zeropage indirect addressing, thanks Mike's point about zeropage indirect addressing is important here, because you're writing things to the screen. You probably plan on moving these things ...

OMG, that made things so much easier, thanks! Thanks, I'll try that out clc ldx #11 ;column (0-21) ldy #10 ;row (0-22) jsr $FFF0 ;plot - set cursor position I've come to appreciate PLOT for various things that don't need optimum speed. It's wonderful simplicity when the alternative is 16-bit math. B...

Got it, thanks. That makes sense. Brian, just to get some facts across: Isn't that how you declare a constant, not a variable? When you are working with a symbolic (cross-)assembler, those symbols being assigned to a value are only relevant at assemble time (i.e., when the assembler builds your prog...

I'll give that a try, thanks You might find it useful to hold your character position as a screen row and column rather than an offset from an absolute address. You can then load the zero page pointers (as shown by chysn) with the address of the screen row, and offset to the column using the y index...

Thanks! Mike's point about zeropage indirect addressing is important here, because you're writing things to the screen. You probably plan on moving these things around. If so, you're likely to abandon your original code in favor of using a couple zeropage locations to store a pointer to the location...

Isn't that how you declare a constant, not a variable? I don't know anything about CBM Prog Studio, but I'm pretty sure that I see why the second one doesn't work. It doesn't matter what's stored at char_p in the least, because your X is stored to whatever address the label is defined as. You can co...

Thanks, I'll try that out clc ldx #11 ;column (0-21) ldy #10 ;row (0-22) jsr $FFF0 ;plot - set cursor position I've come to appreciate PLOT for various things that don't need optimum speed. It's wonderful simplicity when the alternative is 16-bit math. But... keep in mind that X and Y registers are ...

CBM Prog Studio is acting weird with a simple basic program that I have written for the VIC-20. I keep getting errors, they seem to be memory related. I created a simple Space Invader demo with a turret moving back and forth along the bottom under joystick control. I had an Invader marching back and...

Thanks, I'll check this out

Mike wrote: ↑Tue Mar 22, 2022 4:11 pm The BALLPING example in my VICMON primer thread (see second post) shows a more elaborate example use of this address mode.

Thanks for all of the help, I want char_p (should have been more clear - maybe car_pos for character position) to be the start of screen memory (7680) as a variable and store the character "A" there. then if I right on the joystick I could inc car_pos ldx #1 ; char "A" stx car_po...

why does this work: ldx #1 ; code for "A" stx 7680 ; place at first screen location but this does not: ldx #1 ; code for "A" stx char_p ; place at first screen location char_p word 7680 ; invader starting position It should be the same thing, right? Thanks for any help, Brian