Apple-2-SW/apple2_hgr_font_tutorial
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Michaelangel007 2016-01-27 21:18:28 -08:00
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#Apple ]\[ //e HGR Font 6502 Assembly Language Tutorial
Revision: 60, Jan 27, 2016.
Revision: 61, Jan 27, 2016.
# Table of Contents
@ -1540,14 +1540,14 @@ Listing Demo 3a:
1013:AD 00 C0 .2 LDA KEYBOARD ; read A=key
1016:10 FB BPL .2 ; no key?
1018:8D 10 C0 STA KEYSTROBE ; debounce key
101B:C9 88 CMP #$88 ; key == <-- ?
101B:C9 88 CMP #$88 ; key == <-- ? CTRL-H
101D:D0 0A BNE .4 ;
101F:C6 FE DEC glyph ; yes, --glyph
1021:A5 FE .3 LDA glyph ; glyph &= 0x7F
1023:29 7F AND #$7F ;
1025:85 FE STA glyph ;
1027:10 DB BPL .1 ; always branch, draw prev char
1029:C9 95 .4 CMP #$95 ; key == --> ?
1029:C9 95 .4 CMP #$95 ; key == --> ? CTRL-U
102B:D0 05 BNE .5 ;
102D:E6 FE INC glyph ; yes, ++glyph
102F:18 CLC ; always branch