IBM PC CONVERTIBLE Technical Reference page 131

0737 45
0738 C3
0739
INC BP
RET
S23 ENDP
; ADJUST PO INTER
; ALL DONE
V4_POSITION - S26
ENTRY
EXIT
0739
0739 Al 0050 R
073C
073C
53
0730 8B 08
073F 8A C4
0741 F6 26 004A R
0745 01 EO
0747 01 EO
0749 2A FF
074B 03 C3
0740
5B
074E
C3
074F
ENTRY
EXIT
074F
074F 50
0750 50
0751 B4 03
0753 8A 3E 0062
0757 CD 10
0759 58
075A 3C 08
075C 74 52
075E 3C 00
0760 74 57
0762 3C OA
S26
THIS ROUTINE TAKES THE CURSOR POSITION
CONTAINED IN THE MEMORY LOCATION, AND
CONVERTS IT INTO AN OFFSET INTO THE
REGEN BUFFER, ASSUMING ONE BYTE/CHAR.
FOR MEDIUM RESOLUTION GRAPHICS,
THE NUMBER MUST BE DOUBLED.
NO REGISTERS, MEMORY LOCATION
CURSOR_POSN I S USED
AX CONTAINS OFFSET INTO REGEN BUFFER
PROC NEAR
MOV AX, CURSOR_POSN GET CURRENT CURSOR
GRAPH_POSN
LABEL NEAR
S26
PUSH BX SAVE REGISTER
MOV BX,AX SAVE COPY OF CURRENT CURSOR
MOV AL,AH GET ROWS TO AL
MUL BYTE PTR CRLCOLS MULTIPLY BY BYTES/COLUMN
SHL
AX,1 MTPLY
*
4 SINCE 4 ROWS/BYTE
SHL
AX,1
SUB BH, BH
ISOLATE COLUMN VALUE
ADD AX,BX DETERMINE OFFSET
POP BX RECOVER POINTER
RET ALL DONE
ENDP
THIS INTERFACE PROVIDES A TELETYPE LIKE INTERF TO VIDEO
CARD. THE INPUT CHARACTER IS WRITTEN TO CURRENT CURSOR
POSITION, AND THE CURSOR IS MOVED TO NEXT POSITION. IF
CURSOR LEAVES THE LAST COLUMN OF THE FIELD, COLUMN IS SET
TO ZERO, AND THE ROW VALUE IS INCREMENTED. IF ROW VALUE
LEAVES THE FIELD, CURSOR IS PLACED ON LAST ROW, FIRST
COLUMN, AND ENTIRE SCREEN IS SCROLLED UP ONE LINE. WHEN
THE SCREEN IS SCROLLED UP, THE ATTRIBUTE FOR FILLING NEW
BLANKED LINE IS READ FROM THE CURSOR POSITION ON PREVIOUS
LINE BEFORE SCROLL, IN CHARACTER MODE. IN GRAPHICS MODE,
THE 0 COLOR IS USED. FOR BKSP, THE CURSOR COLUMN POSITION
I S DECREMENTED BY 1. I F THE CURSOR COLUMN ISO AND A BKSP
OCCURS CURSOR COLUMN REMAINS O. IT DOES NOT BACKSPACE TO
THE PREVIOUS LINE.
(AL)
=
CHARACTER TO BE WRITTEN
NOTE: BACK SPACE, CR, BELL AND LINE FEED ARE HANDLED
AS COMMANDS RATHER THAN AS DISPLAYABLE GRAPHICS
(BL)
=
FOREGROUND COLOR FOR CHAR WRITE IF CURRENTLY I N A
GRAPHICS MODE
(OS)
=
DATA SEGMENT
ALL REGI STERS SAVED
ASSUME CS: ROMCODE, OS: DATA
WRITE_TTY
PUSH
PUSH
MOV
MOV
INT
POP
AX
AX
PROC NEAR
AH, GELCURSOILINFO
BH,ACTIVE_PAGE
VIDEO_FN
AX
SAVE REGISTERS
SAVE CHAR TO WRITE
READ CURRENT CURSOR POSITION
SET CURRENT ACTIVE PAGE
I NT 10H
RECOVER CHAR
OX NOW HAS THE CURRENT CURSOR POSITION
CMP
JE
CMP
JE
CMP
AL,8
U8
AL ,DOH
U9
AL,OAH
IS IT A BACKSPACE
BACICSPACE
IS IT CARRIAGE RETURN
CAR_RET
IS IT A LINE FEED
2-106 ROM BIOS