Added ca65 source

asm/drawfont.s

@@ -0,0 +1,130 @@
+        __MAIN = $301
+        .include "dos33.inc"
+
+; Listing 11
+
+        HgrLo   = $E5   ; Low  byte Pointer to screen destination
+        HgrHi   = $E6   ; High byte Pointer to screen destination
+        String  = $F0
+        TmpLo   = $F5   ; Low  byte Working pointer to screen byte
+        TmpHi   = $F6   ; High byte Working pointer to screen byte
+        TopHi   = $FD
+        Font    = $6000
+
+;       ORG $0301 ; Listing 8
+DrawHexByte:
+        PHA             ; save low nibble
+        ROR             ; shift high nibble
+        ROR             ; to low nibble
+        ROR             ;
+        ROR             ;
+        JSR DrawHexNib  ; print high nib in hex
+        PLA             ; pritn low  nib in hex
+DrawHexNib:
+        AND #$F         ; base 16
+        TAX             ;
+        LDA NIB2HEX,X   ; nibble to ASCII
+;       ORG $0310 ; Listing 5
+DrawChar:
+        JMP DrawCharCol
+;       ORG $0313 ; Listing 9
+SetCursorRow:
+        LDA HgrLoY,X   ; HgrLoY[ row ]
+        STA TmpLo
+        LDA HgrHiY,X   ; HgrHiY[ row ]
+        CLC
+        ADC HgrHi
+        STA TmpHi
+        RTS
+;       ORG $0321 ; Listing 11
+SetCursorColRow:
+        STX TmpLo
+        LDA HgrLoY,Y    ; HgrLoY[ row ]
+        CLC
+        ADC TmpLo       ; add column
+        STA TmpLo
+        LDA HgrHiY,Y    ; HgrHiY[ row ]
+        CLC             ; \ could optimize this into
+        ADC HgrHi       ; / single ORA HgrHi
+        STA TmpHi
+        RTS
+        NOP             ; pad
+;       ORG $0335 ; Listing 6
+DrawCharColRow:
+        PHA
+        JSR SetCursorRow
+        PLA
+;       ORG $033A ; Listing 7
+DrawCharCol:           ;     A=%PQRstuvw
+        ROL            ; C=P A=%QRstuvw?
+        ROL            ; C=Q A=%Rstuvw?P
+        ROL            ; C=R A=%stuvw?PQ
+        TAX            ;     X=%stuvw?PQ push glyph
+        AND #$F8       ;     A=%stuvw000
+        STA _LoadFont+1; AddressLo = (c*8)
+        TXA            ;     A=%stuvw?PQ pop glyph
+        AND #3         ; Optimization: s=0 implicit CLC !
+        ROL            ; C=s A=%00000PQR and 1 last ROL to get R
+        ADC #>Font     ; += FontHi; Carry=0 since s=0 from above
+        STA _LoadFont+2; AddressHi = FontHi + (c/32)
+;       ORG $034C ; Listing 4a
+_DrawChar1:
+        LDX TmpHi
+        STX TopHi
+;       ORG $0350 ; Listing 1
+_DrawChar:
+        LDX #0
+_LoadFont:              ; A = font[ offset ]
+        LDA Font,X
+        STA (TmpLo),Y   ; screen[col] = A
+        CLC
+        LDA TmpHi       ;
+        ADC #4          ; screen += 0x400
+        STA TmpHi
+        INX
+        CPX #8
+        BNE _LoadFont
+;       ORG $0363 ; Listing 4a
+IncCursorCol:
+        INY
+        LDX TopHi       ; Move cursor back to top of scanline
+        STX TmpHi
+        RTS
+;       ORG $0369 ; Listing 10
+SetCursorColRowYX:
+        JSR SetCursorRow
+        CLC
+        TYA
+        ADC TmpLo
+        STA TmpLo
+        RTS
+;       ORG $037E ; Listing 12
+DrawString:
+         STY String+0
+         STX String+1
+         LDY #0
+_ds1:    LDA (String),Y
+         BEQ _ds2       ; null byte? Done
+         JSR DrawChar   ; or DrawCharCol for speed
+         CPY #40        ; col < 40?
+         BCC _ds1
+_ds2:    RTS
+
+                        ; pad $0385 .. $38F
+        .res $390 - *, $00
+
+;       ORG $0390 ; Listing 8
+NIB2HEX:
+        .byte "0123456789ABCDEF"
+;       ORG $03A0 ; Listing 9a
+HgrLoY:
+        .byte $00,$80,$00,$80,$00,$80,$00,$80
+        .byte $28,$A8,$28,$A8,$28,$A8,$28,$A8
+        .byte $50,$D0,$50,$D0,$50,$D0,$50,$D0
+HgrHiY:
+        .byte $00,$00,$01,$01,$02,$02,$03,$03
+        .byte $00,$00,$01,$01,$02,$02,$03,$03
+        .byte $00,$00,$01,$01,$02,$02,$03,$03
+
+__END:
+