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Cleanuped SetCursorColRow to be consistent
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michaelangel007
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README.md
42
README.md
@ -26,7 +26,7 @@ Revision: 17, Jan 10, 2016.
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* Character Inspector version 2
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* Character Inspector version 3
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* Y Cursor Position
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* Natural Params CursorColRow()
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* Natural Params SetCursorColRow()
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* DrawString()
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* Recap
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* Copy text screen to HGR
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@ -80,7 +80,7 @@ When we are done we will have 6502 assembly code that implements the equivalent
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void DrawCharCol( char c, int col )
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void DrawCharColRow( char c, int col, int row );
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void SetCursorRow( int row );
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void SetCursorColRow( int col, int row );
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void SetCursorColRow3( int col, int row );
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void SetCursorCol( int col );
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void IncCursorCol();
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void DrawHexByte( char c );
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@ -1179,7 +1179,7 @@ Enter in:
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## Natural Params CursorColRow()
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## Natural Params SetCursorColRow()
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Unfortunately, our usage of the X and Y registers are not intuitive. This is due to the limited addressing modes of the 6502. :-/ If the 6502 had a symmetrical indirect zero-page X addressing mode:
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@ -1188,7 +1188,7 @@ Unfortunately, our usage of the X and Y registers are not intuitive. This is due
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We could map the X-register to the natural column (x-axis), and the Y-register to the natural row (y-axis). Alas, we're stuck with the X=row and Y=col unless we wanted to add extra code to "swap" the two.
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```assembly
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; FUNC: CursorColRow() = $0379
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; FUNC: SetCursorColRowYX() = $0379
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; PARAM: Y = col
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; PARAM: X = row
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379:20 28 03 JSR CursorRow
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@ -1198,17 +1198,12 @@ We could map the X-register to the natural column (x-axis), and the Y-register t
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381:85 F5 STA $F5
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383:60
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```
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Enter in:
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379:20 28 03 18 98 65 F5 85 F5 60
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Or are we stuck? Since we're using a function to calculate the destination address let's fix the order.
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We'll need to change the `X` offset in CursorRow() to `Y`;
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We'll need to change the `X` offset in SetCursorColRowXY() to `Y`;
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```assembly
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; FUNC: CursorRow2( row ) = $033B
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; FUNC: SetCursorColRow2( row ) = $033B
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; PARAM: Y = row
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; NOTES: Version 2 !
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328:B9 00 64 LDA $6400,Y ; changed from: ,X
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@ -1225,7 +1220,7 @@ We'll need to change the `X` offset in CursorRow() to `Y`;
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And change the low byte to add `X` instead:
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```assembly
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; FUNC: CursorColRow2( col, row ) = $0379
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; FUNC: SetCursorColRow2( col, row ) = $0379
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; PARAM: X = col
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; PARAM: Y = row
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; NOTES: Version 2 !
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@ -1237,21 +1232,21 @@ And change the low byte to add `X` instead:
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383:60
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```
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This is a little clunky but it is progress. Let's write the new CursorColRow() version with the CursorRow() inlined so we don't have to use a JSR.
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This is a little clunky but it is progress. Let's write the new SetCursorColRow() version with the CursorRow() inlined so we don't have to use a JSR.
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```assembly
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; FUNC: CursorColRow3( col, row ) = $0379
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; FUNC: SetCursorColRow( col, row ) = $0379
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; PARAM: X = column to draw at; $0 .. $27 (Columns 0 .. 39) (not modified)
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; PARAM: Y = row to draw at; $0 .. $17 (Rows 0 .. 23) (not modified)
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; NOTES: Version 3! X and Y is swapped from earlier version!
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; [$F5] = HgrLo[ Y ] + [$E5] + X
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; [$F5] = HgrLo[ Y ] + ScreenLo + X
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379:86 F5 STX $F5
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37B:B9 00 64 LDA $6400,Y ; HgrLo[ row ]
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37B:B9 00 64 LDA HgrLo,Y ; HgrLo[ row ]
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37E:18 CLC
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37F:65 E5 ADC $E5
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381:65 F5 ADC $F5
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381:65 F5 ADC $F5 ; add column
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383:85 F5 STA $F5
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385:B9 18 64 LDA $6418,Y ; HgrHi[ row ]
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385:B9 18 64 LDA HgrHi,Y ; HgrHi[ row ]
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388:18 CLC
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389:65 E6 ADC $E6
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38B:85 F6 STA $F6
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@ -1290,7 +1285,7 @@ And our example to verify that it works:
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; FUNC: DemoDrawString()
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1200:A2 03 LDX #3 ; col = 3
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1202:A0 02 LDY #2 ; row = 2
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1204:20 79 03 JSR CursorColRow3
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1204:20 79 03 JSR SetCursorColRow
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1207:A2 12 LDX >.3 ; High
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1209:A0 0E LDY <.3 ; Low
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120B:4C 8E 03 JMP DrawString
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@ -1442,7 +1437,7 @@ Here's the Pseudo-code to copy the text screen to the HGR Screen:
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{
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SrcTextLo = HgrLo[ row ];
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SrcTextHi = HgrHi[ row ] - 0x1C;
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// CursorColRow( 0, row ) which does:
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// SetCursorColRow( 0, row ) which does:
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DstHgrLo = HgrLo[ row ]
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DstHgrHi = HgrHi[ row ]
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@ -1462,17 +1457,18 @@ And here is the assembly:
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; DATA:
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; $6000.$63FF Font 7x8 Data
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; $6400.$642F HgrLo, HgrHi table for every 8 scanlines
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.ORG $1300
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1300:A9 00 LDA #0
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1302:85 F3 STA row
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1304:85 E5 STA $E5
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1306:A9 20 LDA #20 ; Dest = HGR1 = $2000
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1308:85 E6 STA $E6
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130A:A4 F3 .1 LDY row
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130A:A4 F3 .1 LDY row ; Y = row
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130C:C0 18 CPY #$18 ; 24 is #$18
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130E:B0 20 BCS .3 ; Y >= 24
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1310:A2 00 LDX #0
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1312:86 F2 STX col
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1314:20 79 03 JSR CursorColRow3 ; A = HgrHi[ row ]
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1312:86 F2 STX col ; X = col
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1314:20 79 03 JSR SetCursorColRow ; A = HgrHi[ row ]
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1317:18 CLC ; Convert HgrHi to TextHi byte
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1318:E9 1B SBC #$1B ; A -= 0x1C
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131A:85 F8 STA $F8
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