Apple-2-SW/apple2_hgr_font_tutorial
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Start cleanup 4 byte address disassembly

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michaelangel007 2016-01-11 02:11:04 -08:00
parent 3066eadaf2
commit 329867e140
1 changed files with 17 additions and 16 deletions
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README.md
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@ -1155,28 +1155,29 @@ To select which row to draw at we'll pass that in the X register to our DrawChar
; PARAM: A = glyph to draw
; PARAM: Y = column to draw at; $0 .. $27 (Columns 0 .. 39) (not modified)
; PARAM: X = row to draw at; $0 .. $17 (Rows 0 .. 23) (destroyed)
ORG $0320
320: DrawCharColRow
320:48 PHA
321:20 28 03 JSR SetCursorRow
324:68 PLA
325:4C 3B 03 JMP DrawCharCol
ORG $0320
0320: DrawCharColRow
0320:48 PHA
0321:20 28 03 JSR SetCursorRow
0324:68 PLA
0325:4C 3B 03 JMP DrawCharCol
; FUNC: SetCursorRow( row )
; PARAM: X = row to draw at; $0 .. $17 (Rows 0 .. 23) (not modified)
; INPUT : $E5,$E6 initial pointer to the destination screen scanline
; Note: Must start at every 8 scanlines.
; OUTPUT: $F5,$F5 working pointer to the destination screen scanline
ORG $0328
328:BD 00 64 LDA HgrLoY,X ; HgrLoY[ row ]
32B:18 CLC
32C:65 E5 ADC HgrLo
32E:85 F5 STA TmpLo
330:BD 18 64 LDA HgrHiY,X ; HgrHiY[ row ]
333:18 CLC
334:65 E6 ADC HgrHi
336:85 F6 STA TmpHi
338:60 RTS
ORG $0328
0328: SetCursorRow
0328:BD 00 64 LDA HgrLoY,X ; HgrLoY[ row ]
032B:18 CLC
032C:65 E5 ADC HgrLo
032E:85 F5 STA TmpLo
0330:BD 18 64 LDA HgrHiY,X ; HgrHiY[ row ]
0333:18 CLC
0334:65 E6 ADC HgrHi
0336:85 F6 STA TmpHi
0338:60 RTS
```
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