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Streamlined display character selection.

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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.
This commit is contained in:
Oliver Schmidt 2017-05-23 23:56:57 +02:00
parent c7b1c77367
commit 7d50e73b5b
1 changed files with 36 additions and 23 deletions
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59
drivers/a2vt100.s
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@ -45,8 +45,6 @@ SendStr = telnet_send_string
.include "apple2.inc" .include "apple2.inc"
ControlFlags = $1000
; ************************************* ; *************************************
; * ; *
; * Zeropage ; * Zeropage
@ -1038,39 +1036,29 @@ PrnChr sta xVector ; save char
lda xVector ; restore char lda xVector ; restore char
; -- $80-$ff -- non-ASCII ; -- $80-$ff -- non-ASCII
bpl PC1 bmi PCend ; no output
jmp PCend
; -- $20-$7f -- printable
PC1 cmp #$20
bcc PC2
jmp PCrvs
; -- $00-$1f -- control
PC2 jmp PCend ; no output
; -- handle reverse mode -- ; -- handle reverse mode --
PCrvs ora #$80 ; turn on high bit ldx INVFLG ; reverse mode?
ldy INVFLG bmi PC1 ; normal:$ff, reverse:$3f
cpy #$ff ; normal character display mode? tax
beq PCput lda rtsc,x ; reverse to ScreenCode
cmp #$e0 ; lowercase?
bcc PCmask
and #$7f ; inverse lowercase
jmp PCput jmp PCput
PCmask and INVFLG ; apply normal, inverse, flash PC1 ora #$80 ; normal to ScreenCode
PCput ldx lbPending ; need new line? PCput ldx lbPending ; need new line?
beq PC6 ; no -> skip beq PC2 ; no -> skip
ldx #$00 ; clear pending ldx #$00 ; clear pending
stx lbPending stx lbPending
jsr NewLn jsr NewLn
PC6 tax ; save char PC2 tax ; save char
lda CH ; get crsr col lda CH ; get crsr col
lsr ; col DIV 2 lsr ; col DIV 2
tay tay
txa ; restore char txa ; restore char
bcs PC7 ; odd col? bcs PC3 ; odd col?
bit $c055 bit $c055
PC7 sta (BASL),y ; char to screen PC3 sta (BASL),y ; char to screen
bit $c054 bit $c054
ldy CH ; get crsr col ldy CH ; get crsr col
@ -1484,10 +1472,35 @@ ExitScr
; ************************************* ; *************************************
; * ; *
; * ASCII tables ; * ASCII and ScreenCode tables
; * ; *
; ************************************* ; *************************************
; -------------------------------------
; table reverse to ScreenCode
;
; This tabel is used to convert incoming
; reverse chars.
; -------------------------------------
rtsc;_0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _a _b _c _d _e _f
; --- Control chars - should never appear --------------------------
.byt $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; 0_
.byt $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; 1_
; --- special chars ------------------------------------------------
.byt $20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$2a,$2b,$2c,$2d,$2e,$2f ; 2_
.byt $30,$31,$32,$33,$34,$35,$36,$37,$38,$39,$3a,$3b,$3c,$3d,$3e,$3f ; 3_
; --- capital letters ----------------------------------------------
.byt $00,$01,$02,$03,$04,$05,$06,$07,$07,$09,$0a,$0b,$0c,$0d,$0e,$0f ; 4_
.byt $10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$1a,$1b,$1c,$1d,$1e,$1f ; 5_
; --- lower case letters -------------------------------------------
.byt $60,$61,$62,$63,$64,$65,$66,$67,$68,$69,$6a,$6b,$6c,$6d,$6e,$6f ; 6_
.byt $70,$71,$72,$73,$74,$75,$76,$77,$78,$79,$7a,$7b,$7c,$7d,$7e,$7f ; 7_
; ------------------------------------- ; -------------------------------------
; table keyboard to ASCII ; table keyboard to ASCII
; ;