IBM PC CONVERTIBLE

07FF 8A 1E 0049 R MOV
BL,CRLMODE
0803 2A FF SUB
BH,BH MODE VALUE TO BX
0805 2E: 8A 9F 07CB R
MOV BL,CS:V1[BX]
DETERMINE AMOUNT TO SUBTRACT
080A 2B C3
SUB AX,BX TAKE IT AWAY
080C 8B 1E 004E R MOV
BX,CRLSTART
0810 01 EB
SHR BX,l
0812 2B C3
SUB AX, BX
0814 79 02
JNS V2 IF POSITIVE, DETERMINE MODE
0816 2B CO SUB
AX,AX <0 PLAYS AS 0
DETERMINE MODE OF OPERATION
0818
V2 :
DETERMINEjlODE
0818
B1 03
MOV CL,3
SET *8 SHIFT COUNT
081A 80 3E 0049 R 04 CMP CRLMODE,4
DETERMINE IF GRAPHICS OR ALPHA
081F
72 2A JB
V4
ALPHA_PEN
0821 80 3E 0049 R 07 CMP CRLMODE,7
0826 74 23 JE
V4
ALPHA_PEN
GRAPHICS MODE
0828
B2 28
MOV DL,40
DIVISOR FOR GRAPHICS
082A F6 F2
DIV
DL
DETERMINE ROW(AL) AND COLUMN(AH)
AL RANGE 0-99, AH RANGE 0-39
DETERMINE GRAPHIC ROW POSITION
082C 8A E8
MOV CH,AL
SAVE ROW VALUE IN CH
082E 02 ED
ADD CH,CH
*2 FOR EVEN/ODD FI ELD
0830 8A DC
MOV
BL,AH
COLUMN VALU E TO BX
0832 2A FF
SUB
BH, BH
MUL TI PL Y BY 8 FOR MEDIUM RES
0834
80 3E 0049 R 06
CMP
CRLMODE,6
DETERMINE MEDIUM OR HIGH RES
0839 75 04
JNE
V3
NOLH I GH_RES
083B B1 04 MOV CL,4
SHI FT VALUE FOR HIGH RES
0830 DO E4 SAL AH,l
COL VAL TIMES 2 FOR HIGH RES
083F V3:
NOLHIGH_RES
083F 03 E3 SHL BX,CL
MULTIPLY *16 FOR HIGH RES
DETERMINE ALPHA CHAR POSITION
0841 8A 04 MOV DL,AH
COLUMN VALUE FOR RETURN
0843 8A FO MOV DH,AL
ROW VALUE
0845 DO EE SHR DH,l
DIVIDE BY 4
0847 DO EE SHR DH,l
FOR VALUE IN 0-24 RANGE
0849 EB 12 JMP
SHORT V5
LIGHT _PEN_RETURN_SET
;----- ALPHA MODE ON LIGHT PEN
084B V4:
ALPHA_PEN
084B F6 36 004A R DIV BYTE PTR CRLCOLS
DETERMINE ROW,COLUMN VALUE
084F 8A FO MOV DH,AL
ROWS TO DH
0851 8A 04 MOV DL,AH
COLS TO DL
0853 02 EO
SAL AL,CL MUL TI PL Y ROWS * 8
0855 8A E8 MOV
CH,AL GET RASTER VAL TO RETURN REG
0857 8A DC MOV
BL,AH COLUMN VALUE
0859 32 FF XOR BH, BH
TO BX
085B 03 E3 SAL
BX,CL
0850 V5:
LI GHT _PEN_RETURN_SET
0850 B4 01 MOV AH,l INDICATE EVERTHING SET
085F V6:
LIGHT _PEN_RETURN
085F 52 PUSH OX SAVE RETURN VALUE (IN CASE)
0860 8B 16 0063 MOV OX ,ADDR_6845 GET BASE ADDRESS
0864 83 C2 07 ADD DX,7 POINT TO RESET PARM
0867 EE OUT DX,AL ADDR, NOT DATA, IS IMPORTANT
0868 5A POP OX RECOVER VALUE
0869 V7:
RETURN_NO_RESET
0869 55 PUSH BP
086A 8B EC MOV BP ,SP
GET PTR TO STACK SAVE AREA
086C 89 5E 08 MOV [BP] • BX-POS, BX
SETUP RETURN VALUES IN STACK
086F 89 4E OA MOV [BP] • CX-POS, CX SAVE AREA
0872 89 56 DC MOV [BP] . DX-POS, OX
0875 50 POP BP
0876 E9 016F R JMP
V IDEO_RETURN
0879
READ_LPEN
ENDP
ROM BIOS 2-109