I added commands to Commodore Vic-20 BASIC via software extensions written in 6502 Assembly. This is an original work leveraging my HIRES for C64. REQUIRES 8K expansion at $2000, and 8K expansion at $A000.
Command syntax
COLOR [foreground[+8][,[background][,[border][,auxillary[,inverse]]]]]
COLOR [foreground[+8]] @ x1,y1 [TO x2,y2]
TEXT
HIRES xresolution, yresolution [,fillbyte]
DELAY jiffies
PLOT COLOR ON|OFF
PLOT [NOT|CLR] (@ x1,y1)|(TO x2,y2)... **
PLOT 0|1|2|3 (@ x1,y1)|(TO x2,y2)...
PLOT "ABC" @ x,y [,addr [,width,height [,bytes]]]
RECT [NOT|CLR] [@] x1,y1 TO x2,y2
RECT 0|1|2|3 @ x1,y1 TO x2,y2
SHAPE GET|PUT|OR|XOR|AND|NOT|CLR addr @ x1, y1 TO x2, y2
** only first @ optional, when not multi-color
Demo1 resizing Notes
Keys ,.<> change resolution
Cursor keys adjust screen positioning
RETURN exits
(recommend run in Vice warp mode in emulation except for positioning)
4UPART (demo2)
4x8 font
The PLOT "TEXT" syntax allows for optionally specifying the font address, height, width, and number of bytes to skip between characters (useful when squeezing the font smaller to eliminate whitespace... example 7 lines instead of 8 sacrificing the last line of the font image but skipping 8 bytes because the font is designed with 8 bytes).
The 4x8 font is currently at $B000 (11*4096 decimal), included in the LOADHIRES20 image. It may be optional or moved in the future.
Feel free to make fonts of any size. The font SHAPEs can be any height/width you design. Then use the PLOT command to draw the text on the screen.
Usage
REM REQUIRES 8K expansion at $2000, and 8K expansion at $A000
LOAD"LOADHIRES20",8 : REM LOAD/INIT HIRES EXTENSION
RUN
LOAD"HIRES28",8 : REM DEMO1
RUN
LOAD"4UPART",8 : REM DEMO2
RUN
- LOADHIRES20 is only file needed to install the extensions (but do not modify by conventional means)
- HIRES20.ML is an alternative copy that can be manually loaded and initialized (SYS 40960), but requires additional steps including moving start of BASIC programs (away from 4096-8191) and performing NEW (see LOADHIRES20)
Build notes
- Compiling requires ACME for use with Microsoft Visual Code.
- Also leverages Esshahn/acme-assembly-vscode-template
- Build launches VICE C-64 Emulator so install that too.
- And some manual editing of the development system and configuration files is required (e.g. ACME and VICE locations). See build.sh for use within Visual Code.
- Additional work will be required for non-Windows platforms (but it's easy).
Links: