IBM PC CONVERTIBLE Technical Reference page 124

;----- ADDRESS RETURNED IS MULTIPLIED BY 2 FROM CORRECT VALUE
04DE EB 073C R
CALL
GRAPH_POSN
04El 8B F8 MOV DI,AX ; SAVE RESULT AS DEST ADDRESS
DETERMINE SIZE OF WINDOW
04E3 2B 01
SUB
OX ,CX
04E5
81 C2 0101 ADD DX,101H ADJUST VALUES
04E9
DO E6 SAL DH,l MUL TIPL Y # ROWS BY 4
SINCE 8 VERT DOTS/CHAR
04EB DO E6 SAL DH,l AND EVEN/ODD ROWS
DETERMINE CRT MODE
04ED
80 3E 0049 R 06 CMP CRLMODE,6 TEST FOR MEDIUM RES
04F2
73 04 JNC R7 FIND_SOURCE
MEDIUM RES UP
04F4
DO E2 SAL DL,l ; # COL
*
2 SINCE 2 BYTES/CHAR
04F6 01 E7
SAL 01,1 ; OFFSET *2 SINCE 2 BYTES/CHAR
DETERMINE THE SOURCE ADDRESS IN THE BUFFER
04F8 R7: FIND_SOURCE
04F8 06 PUSH ES GET SEG BOTH POINTING REGEN
04F9 IF
POP OS
04FA
2A ED SUB CH,CH ZERO TO HIGH OF COUNT REG
04FC
DO E3 SAL BL,l MUL TI PL Y NO. OF LI NES BY 4
04FE
DO E3 SAL BL,l
0500
74 20 JZ Rll IF ZERO, BLANK ENTIRE FIELD
0502 8A C3 MOV AL, BL
GET NUMBER OF LINES IN AL
0504 B4 50 MOV AH,80
80 BYTES/ROW
0506 F6 E4 MUL AH DETERMINE OFFSET TO SOURCE
0508 8B F7 MOV SI,DI
SET UP SOURCE
050A 03 FO ADD SI,AX
ADD IN OFFSET TO IT
050C 8A E6 MOV AH,DH NUMBER OF ROWS IN FIELD
050E 2A E3 SUB AH,BL DETERMINE NUMBER TO MOVE
LOOP THROUGH, MOVING ONE ROW AT A TIME, BOTH EVEN & ODD FIELDS
0510
R8: ROW_LOOP
0510 E8 0593 R
CALL R17
MOVE ONE ROW
0513 81 EE IFBO
SUB SI,2000H-80 MOVE TO NEXT ROW
0517 81 EF IFBO
SUB DI,2000H-80
051B FE CC
DEC AH NUMBER OF ROWS TO MOVE
0510 75 Fl
JNZ R8
CONTINUE TILL ALL MOVED
FILL IN THE VACATED LINE(S)
051F
R9: CLEAR-ENTRY
051F 8A C7
MOV AL, BH ATTRIBUTE TO FILL WITH
0521
RlO:
0521 E8 05AC R
CALL R18 CLEAR THAT ROW
0524 81 EF IFBO
SUB DI,2000H-80 POINT TO NEXT LINE
0528 FE CB DEC BL
NUMBER OF LI NES TO FILL
052A 75 F5 JNZ RIO CLEAR_LOOP
052C E9 016F R JMP VIDEO_RETURN EVERYTHING DONE
052F Rll: BLANK_FI ELD
052F 8A DE MOV BL,DH SET BLANK COUNT TO
EVERYTHING IN FIELD
0531 EB EC JMP R9 CLEAR THE FI ELD
0533 GRAPHICS_UP
ENDP
ROM BIOS 2-99