'***************************************************************************
'
'  Smooth Scroling in PowerBASIC V3.0-3.2
'
'  entwickelt von Th.Gohel  FidoNet:   Thomas Gohel@2:2410/330.1
'                           InterNet:  support@pbsound.snafu.de
'                           Homepage:  http://www.snafu.de/~pbsound/
'
'***************************************************************************

FOR i% = 1 TO 25
    LOCATE, 10
    PRINT "Dies ist eine PowerBASIC Scrolling ";
    PRINT "Demonstration by Thomas Gohel"
NEXT i%
SetStart &h1000
Counter% = 8*25
FOR i% = 0 TO Counter%
    LOCATE 1,1: PRINT i%
    Split i%
NEXT i%
FOR i% = Counter% TO 0 STEP -1
    LOCATE 1,1: PRINT i%
    Split i%
NEXT i%
SetStart 0
Split 0
END

'**************************************************************************
'   Aufspalten des Bildschirm's
'**************************************************************************

SUB Split(BYVAL Zeile%) public
        WaitRetrace:                      'Warten auf VerRetrace
        ! mov dx, &h03da
        ! in al, dx
        ! test al, 8
        ! jne WaitRetrace                ;'vorbei??
        SetPalette1:                      'jetzt wieder warten
        ! in al, dx
        ! test al, 8
        ! je SetPalette1
        ! mov bl, Zeile%
        ! xor bh,bh
        ! shl bx,1                        ;*2 wg. Zeilenverdopplung
        ! mov cx,bx
        ! mov dx, &h3d4                   ;CRTC
        ! mov al, &h07                    ;Register 7 (Overflow low)
        ! out dx,al
        ! inc dx
        ! in al,dx
        ! and al,&b11101111               ;Bit 4 mit Bit 8 der Zeile laden
        ! shr cx, 1
        ! shr cx, 1
        ! shr cx, 1
        ! shr cx, 1
        ! and cl,16
        ! or al,cl
        ! out dx,al                     ;und setzen
        ! dec dx
        ! mov al,&h09                    ;Register 9 (Maximum Row Adress)
        ! out dx,al
        ! inc dx
        ! in al, dx
        ! and al,&b10111111              ;Bit 6 mit Bit 9 der Zeile laden
        ! shr bl,1
        ! shr bl,1
        ! shr bl,1
        ! and bl, 64
        ! or  al,bl
        ! out dx,al                        ;und setzen
        ! dec dx
        ! mov al,&h18                      ;Register 18h (Line Compare/Split Screen)
        ! mov ah, Zeile%                   ;restlichen 8 Bit setzen
        ! shl ah,1
        ! out dx,ax
END SUB

'***************************************************************************
'   Startadresse der darzustellenden Bildschirmseite
'***************************************************************************

SUB SetStart(BYVAL Zeile??) public
        LOCAL High?, Low?
        ! mov ax, Zeile??
        ! mov High?, ah
        ! mov Low?, al
        ! mov dx, &h3d4                    ;CRTC
        ! mov al,&h0c                      ;Register 0ch(Linear Starting Adress Middle)
        ! mov ah, High?                    ;Bits 15:8 setzen
        ! out dx,ax                        ;Register 0dh (LSA Low)
        ! mov al,&h0d                      ;Bits 7:0 setzen
        ! mov ah, Low?
        ! out dx,ax
END SUB