joriszwart / chargenxor

chargenxor is a simple tool to transform (XOR) your custom CBM font using the default charset ROM to make it more compressible.

chargenxor

chargenxor is a simple tool to transform (XOR) your custom CBM font using the default charset ROM to make it more compressible.

Usage

$ chargenxor <customfont> <outputfile>

A file called chargen containing the default charset ROM should be available in the current directory.

Sample transformation code

                sei
                lda #$33                ; bank chargen in
                sta $01

                ldx #0
copyfont        lda $d000,x
                eor customfont,x
                sta $2000,x
                lda $d100,x
                eor customfont,x
                sta $2100,x
                inx
                bne copyfont

                lda #$37                ; default banks (basic / kernal / IO)
                sta $01
                cli

Version history

Version	Notes

1.0 | Initial version.