83Plus:RAM:8447 - Revision history

FloppusMaximus: /* Comments */ example comments, linkage, use of 000B

2005-04-21T21:46:42Z

‎Comments: example comments, linkage, use of 000B

AndyJ: /* Synopsis */ linkified GetKey

2005-04-21T19:14:22Z

‎Synopsis: linkified GetKey

Aquanight: Formatting fun

2005-04-21T18:05:35Z

Formatting fun

Aquanight at 18:05, 21 April 2005

2005-04-21T18:05:07Z

New page

[[Category:83Plus:RAM:By Address|8447 - contrast]][[Category:83Plus:RAM:By Name|contrast]]
== Synopsis ==
'''Official Name:''' contrast

'''Memory Address:''' 8447h

'''Length:''' 1 byte.

This area holds the system contrast value. When you press 2nd+Up or 2nd+Down while in a GetKey, GetKey automatically increases or decreases this value and updates the LCD's contrast. The accepted range of this value is 00h ~ 27h.

== Comments ==
Changing this value does not "instantly" update the LCD contrast; you must manually update the LCD. To set the LCD contrast to match the calculator's, add D8h to the read value and output to [[83Plus:Ports:10|Port 10h]]:
<nowiki> ld a, (contrast)
add a, 0D8h
out (10h), a
CALL 000Bh ;Delay required time, or find some other way to waste/use 60 cycles.
</nowiki>

This simple routine sets both the system contrast and the LCD contrast to whatever is in A (valid range is 00~27h, does nothing if out of range).
<nowiki> cp 28h
ret nc ;NC means >= which is bad, so bail out.
ld (contrast), a
push af
add a, 0D8h
out (10h), a
pop af
ret
;Waste/Use ~45 cycles before accessing LCD directly.
</nowiki>

@@ Line 11: / Line 11: @@
 == Comments ==
 Changing this value does not "instantly" update the LCD contrast; you must manually update the LCD. To set the LCD contrast to match the calculator's, add D8h to the read value and output to [[83Plus:Ports:10|Port 10h]]:
-  <nowiki> ld a, (contrast)
+  ld a, (contrast)
   add a, 0D8h
-  out (10h), a
+ CALL 000Bh ; Wait for LCD driver to be ready
- CALL 000Bh ;Delay required time, or find some other way to waste/use 60 cycles.</nowiki>
+  out [[83Plus:Ports:10|(10h)]], a
 This simple routine sets both the system contrast and the LCD contrast to whatever is in A (valid range is 00~27h, does nothing if out of range).
-  <nowiki> cp 28h
+  cp 28h
-  ret nc ;NC means >= which is bad, so bail out.
+  ret nc ; return if the value given is >= 28h
   ld (contrast), a
   push af
   add a, 0D8h
-  out (10h), a
+ CALL 000Bh ; Wait for LCD driver to be ready
   pop af
   ret

@@ Line 5: / Line 5: @@
 '''Memory Address:''' 8447h
-'''Length:''' 1 byte.
+'''Length:''' 1 byte
-This area holds the system contrast value. When you press 2nd+Up or 2nd+Down while in a GetKey, GetKey automatically increases or decreases this value and updates the LCD's contrast. The accepted range of this value is 00h ~ 27h.
+This area holds the system contrast value. When you press 2nd+Up or 2nd+Down while in a [[83Plus:BCALLs:4972|GetKey]], GetKey automatically increases or decreases this value and updates the LCD's contrast. The accepted range of this value is 00h ~ 27h.
 == Comments ==