Difference between revisions of "83Plus:RAM:8447"
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'''Memory Address:''' 8447h | '''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 == | == Comments == | ||
Revision as of 12:14, 21 April 2005
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 Port 10h:
ld a, (contrast) add a, 0D8h out (10h), a CALL 000Bh ;Delay required time, or find some other way to waste/use 60 cycles.
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).
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.
