Added link to Font Tutorial, added HGR and Text address

2016-01-15 03:19:02 -08:00 · 2016-01-15 03:19:02 -08:00 · 6b1be0fa76
parent ab15e2e218
commit 6b1be0fa76
1 changed files with 101 additions and 1 deletions
--- a/Home.md
+++ b/Home.md
@ -1,3 +1,103 @@
 Welcome to the AppleWin wiki!

-Nothing here -yet- but we'll eventually be posting tips & tricks about AppleWin.
+# HGR
+
+* [6502 Assembly HGR Font Tutorial](https://github.com/Michaelangel007/apple2_hgr_font_tutorial)
+
+## = Y to Address =
+
+Given:
+
+    y = abcd efgh
+
+Address is then:
+
+        ---- ---- abcd efgh   INPUT: Y
+        ---- ---- ---- -fgh   &7
+        ---- -fgh ---- ----   * 0x100
+    +   ---f gh-- ---- ----   * 4
+
+        ---- ---- abcd efgh   INPUT: Y
+        ---- ---- ---a bcde   y/8
+        ---- ---- ---- -cde   & 7
+        ---- ---- -cde ----   * 0x10
+    +   ---- --cd e--- ----   * 8
+
+        ---- ---- abcd efgh   INPUT: Y (64 = 2^6)
+        ---- ---- ---- --ab   y/64
+        ---- ---- --ab ----   * 0x10
+        ---- ---- -ab- ----   * 2
+        ---- ---- ---a b---   y/64 * 8
+    +   ---- ---- -aba b---   y/64*0x28   See Note for alt. * 0x28
+
+        -PP- ---- 0000 0000   Graphics page, $20 or $40
+
+    =   0PPf ghcd eaba b000   Address
+
+
+
+C code:
+
+```C
+        int HGR_y_to_address( int y ) {
+            return 0x2000 + (y&7)*0x400 + ((y/8)&7)*0x80 + (y/64)*0x28;
+        }
+```
+
+6502 code:
+
+```assembly
+                            ORG $900
+    0900: B9 00 10       Y2HGRADR LDA   YHgrLo, Y
+    0903: 85 26                   STA   GBASL
+    0905: B9 00 11                LDA   YHgrHi, Y
+    0908: 44 E6                   ORA   $E6
+    090A: 85 27                   STA   GBASH
+    090C: 60                      RTS
+```
+
+# TEXT
+
+## Row to Address
+
+Given:
+
+    y = 000a bcde   (Range 0 .. 23 = $00 .. $17)
+
+        ---- ---- 000a bcde   INPUT: Y
+        000a bcde ---- ----   * 256
+        000a bcd0 ---- ----   & 0xFE
+        0000 abcd ---- ----   / 2
+        0000 00cd ---- ----   & 3
+    +   0000 01cd ---- ----   | 4
+```
+        ---- ---- 000a bcde   INPUT: Y
+        ---- ---- 000a b000   & 0x18
+        ---- ---- e00a b000   = temp
+        ---- ---- 000a b000   & 18
+        ---- ---0 00ab 0000   * 2
+        ---- --00 0ab0 0000   * 2
+    +   ---- --00 eaba b000   | temp
+
+    =   0000 01cd eaba b000   Address
+```
+
+```assembly
+FBC1: 48        577  BASCALC  PHA              ;CALC BASE ADR IN BASL,H
+FBC2: 4A        578           LSR              ;  FOR GIVEN LINE NO
+FBC3: 29 03     579           AND   #$03       ;  0<=LINE NO.<=$17
+FBC5: 09 04     580           ORA   #$04       ;ARG=000ABCDE, GENERATE
+FBC7: 85 29     581           STA   BASH       ;  BASH=000001CD
+FBC9: 68        582           PLA              ;  AND
+FBCA: 29 18     583           AND   #$18       ;  BASL=EABAB000
+FBCC: 90 02     584           BCC   BSCLC2
+FBCE: 69 7F     585           ADC   #$7F
+FBD0: 85 28     586  BSCLC2   STA   BASL
+FBD2: 0A        587           ASL
+FBD3: 0A        588           ASL
+FBD4: 05 28     589           ORA   BASL
+FBD6: 85 28     590           STA   BASL
+FBD8: 60        591           RTS
+```
+
+