Apple-2-SW/apple2_hgr_font_tutorial
1
0
Fork 0
mirror of https://github.com/Michaelangel007/apple2_hgr_font_tutorial.git synced 2024-06-04 22:29:27 +00:00
Code Issues Projects Releases Wiki Activity

Fix EQU alignment

Browse Source
This commit is contained in:
Michaelangel007 2016-01-27 15:57:04 -08:00
parent 6c1a2695e2
commit 5c36f6b288
1 changed files with 22 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
README.md
View File

@ -1,6 +1,6 @@
#Apple ]\[ //e HGR Font 6502 Assembly Language Tutorial
Revision: 56, Jan 27, 2016.
Revision: 57, Jan 27, 2016.
# Table of Contents
@ -696,12 +696,12 @@ How did I know to use $0400 when going to the next line? One quirk of the HGR s
Before we can start a simple `DrawChar(char c)` function, we also first need to assign some zero page memory locations for our static and temporary variables, our 16-bit address of where want to draw to. Since we also have our font data, we need a symbol for that too.
```assembly
HgrLo EQU $E5 ; Low byte Pointer to screen destination
HgrHi EQU $E6 ; High byte Pointer to screen destination
TmpLo EQU $F5 ; Low byte Working pointer to screen byte
TmpHi EQU $F6 ; High byte Working pointer to screen byte
HgrLo EQU $E5 ; Low byte Pointer to screen destination
HgrHi EQU $E6 ; High byte Pointer to screen destination
TmpLo EQU $F5 ; Low byte Working pointer to screen byte
TmpHi EQU $F6 ; High byte Working pointer to screen byte
Font EQU $6000
Font EQU $6000
```
Here's the disassembly of our (hard-coded) DrawChar() program:
@ -1008,7 +1008,7 @@ Wait, you say! There IS a way to solve this problem -- and it doesn't take later
Listing 4a:
```assembly
TopHi EQU $FD
TopHi EQU $FD
ORG $034C
034C: _DrawChar1
@ -1960,22 +1960,22 @@ Now that we have the basic print char working lets extend it to print a C-style
Listing 12:
```assembly
String EQU $F0
String EQU $F0
; FUNC: DrawString( *text )
; PARAM: X = High byte of string address
; PARAM: Y = Low byte of string address
037E: ORG $037E
037E: DrawString
037E:84 F0 STY String+0
0380:86 F1 STX String+1
0382:A0 00 LDY #0
0384:B1 F0 .1 LDA (String),Y
0386:F0 07 BEQ .2 ; null byte? Done
0388:20 10 03 JSR DrawChar ; or DrawCharCol for speed
038B:C0 28 CPY #40 ; col < 40?
038D:90 F5 BCC .1
038F:60 .2 RTS
037E:84 F0 STY String+0
0380:86 F1 STX String+1
0382:A0 00 LDY #0
0384:B1 F0 .1 LDA (String),Y
0386:F0 07 BEQ .2 ; null byte? Done
0388:20 10 03 JSR DrawChar ; or DrawCharCol for speed
038B:C0 28 CPY #40 ; col < 40?
038D:90 F5 BCC .1
038F:60 .2 RTS
```
<hr>
**AppleWin**:
@ -2123,9 +2123,9 @@ And here is the assembly:
; DATA:
; $6000.$63FF Font 7x8 Data
; $6400.$642F HgrLoY, HgrHiY table for every 8 scanlines
1300: Txt EQU $F7
1300: Txt EQU $F7
ORG $1300
1300: CopyTextToHgr
1300: CopyTextToHgr
1300:A9 00 LDA #0
1302:85 F3 STA row
1304:85 E5 STA $E5
@ -2656,9 +2656,9 @@ However each HGR "text" line takes 8 scanlines (since our font cell is 7x8).
We could code this up as:
```assembly
Src EQU $F8
Dst EQU $FA
Tmp EQU $FC
Src EQU $F8
Dst EQU $FA
Tmp EQU $FC
; NOTE: Requires $E6 to be initialized with $20 or $40 for graphics page