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Allow start with active 80-column display.

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With active 80-column display there's no way to activate hires page2. Instead of directly fiddling with 80COLSTORE it seems the cleanest way to disable the 80-column display via the official firmware entry point.

The ProDOS 8 Technical Reference Manual states in chapter 5.3.1.3 - 80-Column Text Card:
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80-column text cards -- and other Apple IIe features -- can be turned off
using the following sequence of instructions:

 LDA #$15     ;Character that turns off video firmware
 JSR $C300   ;Print it to the video firmware
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Oliver Schmidt 2020-01-11 13:35:34 +01:00 committed by GitHub
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commit 67b6897fd0
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src/apple2.loader/loader.s
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@ -111,8 +111,15 @@ PRESS_ANY_KEY:
sta READ_REF
sta CLOSE_REF
; Turn off 80-column firmware
lda VERSION
cmp #$06 ; //e ?
bne :+
lda #$15
jsr $C300
; Switch to hires page 2
bit TXTCLR
: bit TXTCLR
bit MIXCLR
bit HISCR
bit HIRES