Hacking Microsoft BASIC
New video! In this one, I modify the Microsoft BASIC code that's running on the 6502 computer to add some new instructions. Specifically, I add instructions for printing to and manipulating the LCD screen that's already part of the computer.
As always, thanks for your support and let me know if anything is unclear or if there are any other issues you see before I release this publicly.
Thanks again!
-Ben
Comments (12)
Ofcourse, now the breadboard computer works with WozMon and MsBasic and lcd write commands are implemented, what else can be still be done? If I may suggest implementing a SPI interface connecting to a SD-card? And after that ofcourse adding a LOAD and SAVE command to Basic.
Yes! SPI load & save, followed by interfacing to the world's worst video card!
So, do you want to build a bootstrap to directly get into basic (without the parameters) and then have a CALL command that dumps out to WozMon?
@Tim Tom - I have not yet watched this episode, but I was just thinking about this same thing. I can imagine Ben thinking several months ago, "Gee, I'd love to kill a Wompus. But, an emulator is just wrong, and I don't want to fix old faulty hardware. So, what could I do. Hmmm...."
It’s amazing looking from this episode back to where it all started. I’ve always been curious how much of it was planned/mapped out when it started. Did you know you’d eventually be running wozmon/basic on the thing when you were building a clock from 555 timers?
My hope was definitely to get BASIC running on it from the beginning, but I didn't exactly have the entire path mapped out of how to get there. That was a very distant goal at the time. The plan at the beginning was really just that I wanted to cover a few things like the LCD or keyboard that weren't practical on the SAP 8-bit CPU. I figured the 6502 would be a better platform for those videos.
Using character codes to clear the screen and move the cursor would also be an interesting experiment.
Thanks, Ben. This is a fantastic episode :)
This is awesome, Ben! One of my favourite videos of yours!
Nice! I love how easy it is to add commands. I would have loved to be able to do this when I learned Assembly way back in collage (early 90s). For the next video and because clearing the screen is such a common thing to do, maybe also add an LCDCLS command.
Unless I missing something (ver possible) this works for me: in lcd.s: LCDCLEAR: lda #%00000001 ; clear display jsr lcd_instruction rts and in token.s: .ifdef EATER keyword_rts "LCDCMD", LCDCMD keyword_rts "LCDPRINT", LCDPRINT keyword_rts "LCDCLEAR", LCDCLEAR .endif Seems to working well.
Woohoo!!!! This is what I've been waiting for! A thousand thanks.