IBM PC CONVERTIBLE Technical Reference page 127

ASSUME CS: ROMCODE, OS: DATA, ES: DATA
05BD
GRAPH I CS_WR ITE PROC
NEAR
05BD
B4 00
MOV AH,O ; ZERO TO HIGH OF CODE POINT
05BF 50 PUSH
AX
; SAVE CODE POINT VALUE
DETERMINE POSITION IN REGEN BUFFER TO PUT CODE POINTS
05CO E8 0739
CALL
S26 ; FIND LOC IN REGEN BUFFER
05C3
8B F8
MOV DI,AX
; REGEN POINTER IN 01
DETERMINE REGION TO GET CODE POINTS FROM
05C5 58
POP
AX ; RECOVER CODE POINT
05C6 IE PUSH OS
05C7 2B F6
SUB SI,SI
05C9 8E DE MOV OS ,SI
ASSUME OS :ABSO
05CB 3C 80 CMP AL,80H
IF IT IS IN SECOND HALF
05CD 73 07
JAE SO JUMP
05CF C5 36 0110
LOS SI,CSELPTR
IT'S IN FIRST HALF
0503 EB 07 90 JMP
SI
0506 2C 80
SO: SUB AL,80H ZERO ORIGIN FOR SECOND HALF
0508 C5 36 007C LOS SI, EXLPTR
GET POINTER TO 2ND HALF
05DC 8C DA
SI : MOV DX,DS SAVE THE SEGMENT OF THE TBL
ASSUME DS:DATA
05DE IF
POP OS RECOVER DATA SEGMENT
05DF 52 PUSH OX
SAVE TABLE SEGMENT ON STACK
DETERMINE GRAPHICS MODE IN OPERATION
05EO
S2: DETERMINE-MODE
05EO 01 EO SAL AX,1
MUL TI PL Y CODE PO I NT
05E2
01 EO SAL
AX,1 VALUE BY 8
05E4 01 EO SAL
AX,1
05E6 03 FO
ADD SI,AX
SI HAS OFFSET OF CODES
05E8 80 3E 0049 R 06 CMP
CRLMODE,6
05ED
IF POP OS
RECOVER TBL POINTER SEGMENT
05EE 72 2C
JC
S7 TEST FOR MEDIUM RESOLUTION
HIGH RESOLUTI ON MODE
05FO S3 :
HIGH_CHAR
05FO 57 PUSH
01
SAVE REGEN POINTER
05F! 56 PUSH SI
SAVE CODE POINTER
05F2
B6 04 MOV DH,4
NUMBER OF TIMES THROUGH LOOP
05F4
S4:
05F4
AC LODSB GET BYTE FROM CODE POINTS
05F5 F6 C3 80 TE5T BL,80H
SHOULD WE USE THE FUNCTION
05F8 75 16
JNZ 56 TO PUT CHAR IN
05FA AA
STOSB STORE IN REGEN BUFFER
05FB AC LOD5B
05FC
55:
05FC 26: 88 85 IFFF MOV ES: [DI+2000H-l] ,AL ; STORE IN SECOND HALF
0601 83 C7 4F
ADD 01,79 MOVE TO NEXT ROW IN REGEN
0604 FE CE
DEC DH
DONE WITH LOOP
0606 75 EC JNZ 54
0608 5E POP
51
0609 5F
POP 01 RECOVER REGEN POINTER
060A 47
INC
01 POINT TO NEXT CHAR POSITION
060B E2 E3 LOOP
S3 MORE CHARS TO WRITE
0600 E9 016F R
JMP VIDEO_RETURN
0610 56:
0610 26: 32 05
XOR AL,ES:[DI] EXCLUSIVE OR WITH CURRENT
0613 AA
STOSB
5TORE THE CODE POINT
0614 AC LODSB AGAI N FOR ODD FI ELD
0615 26: 32 85 IFFF XOR
AL,ES: [DI+2000H-l]
061A
EB EO JMP S5 BACK TO MAINSTREAM
;----- MEDIUM RESOLUTION WRITE
061C 57 : MED_RES_WRITE
061C 8A 03
MOV DL,BL SAVE HIGH COLOR BIT
061E 01 E7
5AL 01,1
OFF5ET*2 SINCE 2 BYTE5/CHAR
0620 E8 06F7 CALL S19 EXPAND BL TO FULL WORD
2-102 ROM BIOS