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21
applesoft/spc/README.md
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@ -37,25 +37,25 @@ To understand what's happening here, you need to know how characters are printed
The Applesoft general routine to print characters on screen is in `$DB5C` and is named `OUTDO`.
Here's the routine, taken from [S-C documentor website](http://www.txbobsc.com/scsc/scdocumentor/).
```assembly
1950 * PRINT CHAR FROM (A)
1960 *
1970 * NOTE: POKE 243,32 ($20 IN $F3) WILL CONVERT
1980 * OUTPUT TO LOWER CASE. THIS CAN BE CANCELLED
1990 * BY NORMAL, INVERSE, OR FLASH OR POKE 243,0.
2000 *--------------------------------
DB5C- 09 80 2010 OUTDO ORA #$80 PRINT (A)
DB5E- C9 A0 2020 CMP #$A0 CONTROL CHR?
DB60- 90 02 2030 BCC .1 SKIP IF SO
DB62- 05 F3 2040 ORA FLASH.BIT =$40 FOR FLASH, ELSE $00
DB64- 20 ED FD 2050 .1 JSR MON.COUT "AND"S WITH $3F (INVERSE), $7F (FLASH)
DB5C- 09 80 2010 OUTDO ORA #$80 PRINT (A)
DB5E- C9 A0 2020 CMP #$A0 CONTROL CHR?
DB60- 90 02 2030 BCC .1 SKIP IF SO
DB62- 05 F3 2040 ORA FLASH.BIT =$40 FOR FLASH, ELSE $00
DB64- 20 ED FD 2050 .1 JSR MON.COUT "AND"S WITH $3F (INVERSE), $7F (FLASH)
DB67- 29 7F 2060 AND #$7F
DB69- 48 2070 PHA
DB6A- A5 F1 2080 LDA SPEEDZ COMPLEMENT OF SPEED #
DB6C- 20 A8 FC 2090 JSR MON.WAIT SO SPEED=255 BECOMES (A)=1
DB6A- A5 F1 2080 LDA SPEEDZ COMPLEMENT OF SPEED #
DB6C- 20 A8 FC 2090 JSR MON.WAIT SO SPEED=255 BECOMES (A)=1
DB6F- 68 2100 PLA
DB70- 60 2110 RTS
```
The routine is called with the accumulator containing the character to print every time Applesoft needs to print something (like when using `PRINT` or `INPUT` or ... `SPC` !)
The routine that will effectively print the character on screen is `COUT` (in `$FDED`here named `MON.COUT`) but the `OUTDO` routine here is the pre-treatment of the character to print.
@ -139,7 +139,7 @@ Remember that not all characters are printable in FLASH or INVERSE.
This little program will demonstrate what we learned here.
It will fill the screen with one kind of character, using four `SPC` statements with a parameter of 240.
```basic
10 HOME
20 X = 255: Y=0: REM INIT VALUES
30 POKE 243,0: REM RESET ORA MASK
@ -159,6 +159,7 @@ It will fill the screen with one kind of character, using four `SPC` statements
170 PRINT SPC(240)
180 PRINT SPC(240)
190 GOTO 20
```
<img src="spc6.png">
# HAPPY CODING !