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Streamlined display character selection.
The reverse characters of the alternate char set are place in a somewhat strange arrangement in the Apple II character ROM. This is because of backward compatibility with the standard char set. Therefore it seems more efficient and hopefully easier to understand to use a table to select them.
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@ -45,8 +45,6 @@ SendStr = telnet_send_string
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.include "apple2.inc"
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ControlFlags = $1000
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; *************************************
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; *
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; * Zeropage
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@ -1038,39 +1036,29 @@ PrnChr sta xVector ; save char
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lda xVector ; restore char
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; -- $80-$ff -- non-ASCII
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bpl PC1
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jmp PCend
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; -- $20-$7f -- printable
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PC1 cmp #$20
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bcc PC2
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jmp PCrvs
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; -- $00-$1f -- control
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PC2 jmp PCend ; no output
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bmi PCend ; no output
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; -- handle reverse mode --
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PCrvs ora #$80 ; turn on high bit
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ldy INVFLG
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cpy #$ff ; normal character display mode?
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beq PCput
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cmp #$e0 ; lowercase?
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bcc PCmask
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and #$7f ; inverse lowercase
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ldx INVFLG ; reverse mode?
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bmi PC1 ; normal:$ff, reverse:$3f
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tax
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lda rtsc,x ; reverse to ScreenCode
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jmp PCput
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PCmask and INVFLG ; apply normal, inverse, flash
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PC1 ora #$80 ; normal to ScreenCode
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PCput ldx lbPending ; need new line?
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beq PC6 ; no -> skip
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beq PC2 ; no -> skip
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ldx #$00 ; clear pending
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stx lbPending
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jsr NewLn
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PC6 tax ; save char
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PC2 tax ; save char
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lda CH ; get crsr col
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lsr ; col DIV 2
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tay
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txa ; restore char
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bcs PC7 ; odd col?
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bcs PC3 ; odd col?
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bit $c055
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PC7 sta (BASL),y ; char to screen
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PC3 sta (BASL),y ; char to screen
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bit $c054
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ldy CH ; get crsr col
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@ -1484,10 +1472,35 @@ ExitScr
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; *************************************
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; *
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; * ASCII tables
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; * ASCII and ScreenCode tables
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; *
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; *************************************
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; -------------------------------------
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; table reverse to ScreenCode
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;
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; This tabel is used to convert incoming
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; reverse chars.
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; -------------------------------------
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rtsc;_0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _a _b _c _d _e _f
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; --- Control chars - should never appear --------------------------
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.byt $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; 0_
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.byt $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; 1_
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; --- special chars ------------------------------------------------
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.byt $20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$2a,$2b,$2c,$2d,$2e,$2f ; 2_
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.byt $30,$31,$32,$33,$34,$35,$36,$37,$38,$39,$3a,$3b,$3c,$3d,$3e,$3f ; 3_
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; --- capital letters ----------------------------------------------
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.byt $00,$01,$02,$03,$04,$05,$06,$07,$07,$09,$0a,$0b,$0c,$0d,$0e,$0f ; 4_
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.byt $10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$1a,$1b,$1c,$1d,$1e,$1f ; 5_
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; --- lower case letters -------------------------------------------
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.byt $60,$61,$62,$63,$64,$65,$66,$67,$68,$69,$6a,$6b,$6c,$6d,$6e,$6f ; 6_
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.byt $70,$71,$72,$73,$74,$75,$76,$77,$78,$79,$7a,$7b,$7c,$7d,$7e,$7f ; 7_
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; -------------------------------------
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; table keyboard to ASCII
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;
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