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Cleanuped SetCursorColRow to be consistent

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michaelangel007 2016-01-10 19:53:29 -08:00
parent a4bf267c94
commit 94b3bc81fe
1 changed files with 28 additions and 32 deletions
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README.md
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@ -26,7 +26,7 @@ Revision: 17, Jan 10, 2016.
* Character Inspector version 2
* Character Inspector version 3
* Y Cursor Position
* Natural Params CursorColRow()
* Natural Params SetCursorColRow()
* DrawString()
* Recap
* Copy text screen to HGR
@ -80,7 +80,7 @@ When we are done we will have 6502 assembly code that implements the equivalent
void DrawCharCol( char c, int col )
void DrawCharColRow( char c, int col, int row );
void SetCursorRow( int row );
void SetCursorColRow( int col, int row );
void SetCursorColRow3( int col, int row );
void SetCursorCol( int col );
void IncCursorCol();
void DrawHexByte( char c );
@ -1179,7 +1179,7 @@ Enter in:
![Screenshot 16](pics/hgrfont_16.png?raw=true)
## Natural Params CursorColRow()
## Natural Params SetCursorColRow()
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:
@ -1188,7 +1188,7 @@ Unfortunately, our usage of the X and Y registers are not intuitive. This is due
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.
```assembly
; FUNC: CursorColRow() = $0379
; FUNC: SetCursorColRowYX() = $0379
; PARAM: Y = col
; PARAM: X = row
379:20 28 03 JSR CursorRow
@ -1198,17 +1198,12 @@ We could map the X-register to the natural column (x-axis), and the Y-register t
381:85 F5 STA $F5
383:60
```
Enter in:
379:20 28 03 18 98 65 F5 85 F5 60
Or are we stuck? Since we're using a function to calculate the destination address let's fix the order.
We'll need to change the `X` offset in CursorRow() to `Y`;
We'll need to change the `X` offset in SetCursorColRowXY() to `Y`;
```assembly
; FUNC: CursorRow2( row ) = $033B
; FUNC: SetCursorColRow2( row ) = $033B
; PARAM: Y = row
; NOTES: Version 2 !
328:B9 00 64 LDA $6400,Y ; changed from: ,X
@ -1225,7 +1220,7 @@ We'll need to change the `X` offset in CursorRow() to `Y`;
And change the low byte to add `X` instead:
```assembly
; FUNC: CursorColRow2( col, row ) = $0379
; FUNC: SetCursorColRow2( col, row ) = $0379
; PARAM: X = col
; PARAM: Y = row
; NOTES: Version 2 !
@ -1237,21 +1232,21 @@ And change the low byte to add `X` instead:
383:60
```
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.
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.
```assembly
; FUNC: CursorColRow3( col, row ) = $0379
; FUNC: SetCursorColRow( col, row ) = $0379
; PARAM: X = column to draw at; $0 .. $27 (Columns 0 .. 39) (not modified)
; PARAM: Y = row to draw at; $0 .. $17 (Rows 0 .. 23) (not modified)
; NOTES: Version 3! X and Y is swapped from earlier version!
; [$F5] = HgrLo[ Y ] + [$E5] + X
; [$F5] = HgrLo[ Y ] + ScreenLo + X
379:86 F5 STX $F5
37B:B9 00 64 LDA $6400,Y ; HgrLo[ row ]
37B:B9 00 64 LDA HgrLo,Y ; HgrLo[ row ]
37E:18 CLC
37F:65 E5 ADC $E5
381:65 F5 ADC $F5
381:65 F5 ADC $F5 ; add column
383:85 F5 STA $F5
385:B9 18 64 LDA $6418,Y ; HgrHi[ row ]
385:B9 18 64 LDA HgrHi,Y ; HgrHi[ row ]
388:18 CLC
389:65 E6 ADC $E6
38B:85 F6 STA $F6
@ -1290,7 +1285,7 @@ And our example to verify that it works:
; FUNC: DemoDrawString()
1200:A2 03 LDX #3 ; col = 3
1202:A0 02 LDY #2 ; row = 2
1204:20 79 03 JSR CursorColRow3
1204:20 79 03 JSR SetCursorColRow
1207:A2 12 LDX >.3 ; High
1209:A0 0E LDY <.3 ; Low
120B:4C 8E 03 JMP DrawString
@ -1442,7 +1437,7 @@ Here's the Pseudo-code to copy the text screen to the HGR Screen:
{
SrcTextLo = HgrLo[ row ];
SrcTextHi = HgrHi[ row ] - 0x1C;
// CursorColRow( 0, row ) which does:
// SetCursorColRow( 0, row ) which does:
DstHgrLo = HgrLo[ row ]
DstHgrHi = HgrHi[ row ]
@ -1462,29 +1457,30 @@ And here is the assembly:
; DATA:
; $6000.$63FF Font 7x8 Data
; $6400.$642F HgrLo, HgrHi table for every 8 scanlines
.ORG $1300
1300:A9 00 LDA #0
1302:85 F3 STA row
1304:85 E5 STA $E5
1306:A9 20 LDA #20 ; Dest = HGR1 = $2000
1306:A9 20 LDA #20 ; Dest = HGR1 = $2000
1308:85 E6 STA $E6
130A:A4 F3 .1 LDY row
130C:C0 18 CPY #$18 ; 24 is #$18
130E:B0 20 BCS .3 ; Y >= 24
130A:A4 F3 .1 LDY row ; Y = row
130C:C0 18 CPY #$18 ; 24 is #$18
130E:B0 20 BCS .3 ; Y >= 24
1310:A2 00 LDX #0
1312:86 F2 STX col
1314:20 79 03 JSR CursorColRow3 ; A = HgrHi[ row ]
1317:18 CLC ; Convert HgrHi to TextHi byte
1318:E9 1B SBC #$1B ; A -= 0x1C
1312:86 F2 STX col ; X = col
1314:20 79 03 JSR SetCursorColRow ; A = HgrHi[ row ]
1317:18 CLC ; Convert HgrHi to TextHi byte
1318:E9 1B SBC #$1B ; A -= 0x1C
131A:85 F8 STA $F8
131C:B9 00 64 LDA $6400, Y ; A = HgrLo[ row ]
131C:B9 00 64 LDA $6400, Y ; A = HgrLo[ row ]
131F:85 F7 STA $F7
1321:A4 F2 LDY col
1323:B1 F7 .2 LDA ($F7),Y
1325:20 10 03 JSR PrintChar
1328:C0 28 CPY #$28 ; 40 is #$18
132A:90 F7 BCC .2 ; Y < 40
1328:C0 28 CPY #$28 ; 40 is #$18
132A:90 F7 BCC .2 ; Y < 40
132C:E6 F3 INC row
133E:D0 DA BNE .1 ; always
133E:D0 DA BNE .1 ; always
1330:60 .3 RTS
```