IBM PC CONVERTIBLE Technical Reference page 118

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E9 016F R
JMP VIDEO_RETURN
N7: BlANLFIElD
BA DE
MOV Bl,DH GET ROW COUNT
EB DC
JMP N3 GO CLEAR THAT AREA
SCROll_UP ENDP
HANDLE COMMON SCROll SET UP HERE
SCROll_POS ITI ON PROC NEAR
E8 02E6 R
CAll POSITION CONVERT TO REGEN POINTER
03 06 004E R ADD AX, CRLSTART OFFSET OF ACTIVE PAGE
8B F8
MOV DI,AX TO ADDRESS FOR SCROll
8B FO
MOV SI,AX FROM ADDRESS FOR SCROll
2B 01
SUB DX,CX OX
=
#ROWS, #COlS IN BLOCK
FE C6
INC DH
FE C2 INC Dl
INCREMENT FOR 0 ORIGIN
32 ED XOR CH,CH
SET HIGH BYTE OF CNT TO ZERO
8B 2E 004A R
MOV BP ,CRLCOlS GET NO. OF COlS IN DISPLAY
03 ED ADD BP, BP
TIMES 2 FOR ATTRI BUTE BYTE
8A C3
MOV Al, Bl GET LINE COUNT
F6 26 004A R MUl
BYTE PTR CRLCOlS FIND OFFSET TO FROM ADDRESS
03 CO
06
IF
80 FB 00
C3
8A CA
56
57
F3/ A5
5F
5E
C3
8A CA
57
F3/ AB
5F
C3
ADD AX,AX
*2 FOR ATTRIBUTE BYTE
PUSH ES
ESTAB ADDSSNG TO REGEN BFR
POP OS
FOR BOTH POINTERS
CMP Bl,O
a
SCROll MEANS BLANK FI ElD
RET
RETURN WITH FLAGS SET
SCROll_POS IT I ON ENDP
;----- MOVE_ROW
NI0 PROC NEAR
MOV Cl,Dl
GET # OF COlS TO MOVE
PUSH SI
PUSH
01 SAVE START ADDRESS
REP MOVSW MOVE THAT LINE ON SCREEN
POP
01
POP SI
RECOVER ADDRESSES
RET
NI0
ENDP
; ----- CLEAR_ROW
Nll PROC NEAR
MOV Cl,Dl
GET # COLUMNS TO CLEAR
PUSH
01
REP STOSW
STORE THE FIll CHARACTER
POP 01
RET
Nll
ENDP
SCROll_DOWN
INPUT
OUTPUT
THIS ROUTINE MOVES THE CHARACTERS WITHIN A
DEFINED BLOCK DOWN ON THE SCREEN, FILLING THE
TOP LINES WITH A DEFINED CHARACTER
(Al)
=
NUMBER OF LINES TO SCROll
(CX)
=
UPPER lEFT CORNER OF REGION
(OX)
=
lOWER RIGHT CORNER OF REGION
(BH)
=
FIll CHARACTER
(AH)
=
CURRENT CRT MODE
(OS)
=
DATA SEGMENT
(ES)
=
REGEN SEGMENT
NONE -- SCREEN IS SCROllED
PROC NEAR
037A FD
SCROll_DOWN
STD ; DIRECTION FOR SCROll DOWN
ROM BIOS 2-93