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(BIOS FOR THE IBM PERSONAL COMPUTER XTl
11/08/82
;
AL = DOT VALUE READ, RIGHT JUSTIFIED, READ ONLY
.
----------------------------------------------------------------
5-157
I S TH I S BW CARD
IS THIS GRAPHICS
SAVE ON STACK
SAVE WR I TE COUNT
GET STATUS
I S IT LOW
WA I T UNT I LIT IS
NO MORE INTERRUPTS
SAVE DOT VALUE
TWICE
DETERM I NE BYTE POS I T I ON OF THE DOT
SH I FT TO SET UP THE BI TS FOR OUTPUT
STR I P OFF THE OTHER BITS
GET THE CURRENT BYTE
RECOVER XOR FLAG
I S IT ON
YES,
XOR THE DOT
SET THE MASK TO REMOVE THE
INDICATED BITS
OR
I N THE NEW VALUE OF THOSE BI TS
FINISH DOT
RESTORE THE BYTE I N MEMORY
DETERM I NE BYTE
pas
I T I ON OF DOT
GET THE BYTE
MASK OFF THE OTHER BITS I N THE BYTE
LEFT JUSTIFY THE VALUE
GET NUMBER OF BITS
IN RESULT
RIGHT JUST I FY THE RESULT
RETURN FROM V IDEO 10
GET BASE ADDRESS
POINT AT STATUS PORT
RETURN FROM V IDEO 10
XOR DOT
EXC[US I VE OR THE DOTS
FIN I SH UP THE WR I T I NG
ADDRESS TO 0 I
WR ITE COUNT
BL HAS CHAR TO WR I TE
WR ITE_LOOP
GET STATUS
I S IT HIGH
; WAIT UNTIL IT IS
; RECOVER CHAR
PUT THE CHAR
1 ATTR
,
I NTERRUPTS BACK ON
; BUMP PO I NTER PAST ATTR IBUTE
;
AS MANY TIMES AS REQUESTED
NEAR
CS: CODE ,OS: DATA ,ES :DATA
PROC
NEAR
R3
AL,ES: [SI]
AL,AH
AL,CL
CL,DH
AL,CL
V IDEO RETURN
ENDP -
AL,DX
AL,I
PI3
AL,BL
ES: [SI] ,AL
AX
V IDEO_RETURN
AL,DX
AL,I
P12
OX, ADDR 6845
DX,6
-
AL,CL
RI
ENDP
PROC
AX
AX
R3
AL,CL
AL,AH
CL,ES:
[s
I]
BX
BL,80H
R2
AH
CL,AH
AL,CL
AX
CX
FIND POSITION
DI,BX
CX
BX
IN
TEST
JNZ
CLI
MOV
ADD
MOV
POP
JMP
PUSH
PUSH
CALL
MOV
POP
POP
PC-XT System BIOS (11/08/82)
INPUT
WR I TE C CURRENT
-TH I S ROUT I NE WR I TES THE CHARACTER AT
THE CURRENT CURSOR POS I TI ON,
ATTR IBUTE
UNCHANGED
( AH)
= CURRENT CRT MODE
(BH)
= 01 SPLAY PAGE
(CX)
= COUNT OF CHARACTERS TO WR I TE
( ALl
= CHAR TO WR I TE
(OS)
= DATA SEGMENT
(ES)
= REGEN SEGMENT
OUTPUT
NONE
EXIT
READ DOT
- -
WR I TE DOT
THESE ROUT I NES WILL WR I TE A DOT, OR READ THE DOT AT
THE
I NO I CATED LOCA T I ON
ENTRY --
OX = ROW
(0 - 199)
(THE ACTUAL VALUE DEPENDS ON THE MODE)
CX = COLUMN
( 0-639)
( THE VALUES ARE NOT RANGE CHECKED)
AL = DOT VALUE TO WRITE
(1,2 OR 4 BITS DEPENDING ON MODE,
REQ'D FOR WRITE DOT ONLY, RIGHT JUSTIFIED)
BIT 1 OF AL= 1 I NO I CATES XOR THE VALUE I NTO THE LOCATION
OS = DATA SEGMENT
ES = REGEN SEGMENT
; ----- WA IT FOR HOR I ZONTAL RETRACE
IN
TEST
JZ
MOV
STOSB
STI
INC
01
LOOP
PI 1
JMP
V IDEO RETURN
WR I TE_C_CURRENT ENDP -
.
------------------------------------------------
WR I TE C CURRENT PROC
NEAR
-
-CMP
AH,4
JC
Pl0
CMP
AH,1
JE
PIO
JMP
GRAPHICS_WRITE
XOR
JMP
WR I TE_DOT
WR ITE DOT
-
PUSH
PUSH
CALL
SHR
AND
MOV
POP
TEST
JNZ
NOT
AND
OR
ASSUME
READ DOT
-
CALL
MOV
AND
SHL
MOV
ROL
JMP
READ_DOT
Pl0:
P12:
P13:
Pll :
4052
4053
4054
4055
4056
4051
4058
4059
4060
4061
4062
4063
4064
4065
4066
4061
4068
4069
4010
4011
4012
4013
4014
4015
4016
4011
4018
4019
4080
4081
4082
4083
4084
4085
4086
4081
4088
4089
4090
4091
4092
4093
4094
4095
4096
4091
4098
4099
4100
4101
4102
4103
4104
4105
4106
4101
4108
4109
4110
4111
4112
4113
4114
4115
4116
4111
4118
4119
4120
4121
4122
4123
4124
4125
4126
4121
4128
4129
4130
4131
4132
4133
4134
4135
4136
4131
4138
4139
4140
4141
4142
Rl:
4143
4144
4145
4146
R2:
4141
4148
4149
LOC OBJECT
F402 8B166300
F406 83C206
F409
F409 EC
F40A A801
F40C 15FB
F40E FA
F40F
F40F EC
F410 A801
F412 14FB
F414 8AC3
F416 AA
F411 FB
F418 41
F419 E2E1
F41B E9A1FD
F42F
F42F 50
F430 50
F431 E81EOO
F434 D2E8
F436 22C4
F438 268AOC
F43B 5B
F43C F6C380
F43F 1500
F441 F6D4
F443 22CC
F445 OAC 1
F441
F441 268804
F44A 58
F44B E911FD
F44E
F44E 32C 1
F450 EBF5
F41E
F41E E83100
F421
268A04
F424 22C4
F426 D2EO
F428 8ACE
F42A D2CO
F42C E996FD
F3EC
F3EC 80FC04
F3EF 1208
F3FI
80FC01
F3F4 1403
F3F6 E91FO 1
F3F9
F3F9 50
F3FA 51
F3FB E8AOFF
F3FE 8BFB
F400 59
F401
5B
F402
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