IBM PC CONVERTIBLE

07CO 75 ES
07C2 EB BC
07C4
07C4
B3 02
07C6 ES 0000 E
07C9 EB DB
07CB
JNE
U6 YES, SCROLL THE SCREEN
JMP UI NO, JUST SET THE CURSOR
BELL FOUND
Ull:
MOV BL ,2
SET UP COUNT FOR BEEP
CALL BEEP SOUND THE POD BELL
JMP
U5 TTLRETURN
WRITE_TTY
ENDP
LIGHT PEN
ON ENTRY
ON EXIT
THIS ROUTINE TESTS THE LIGHT PEN SWITCH AND THE LIGHT
PEN TRIGGER. IF BOTH ARE SET, THE LOCATION OF THE LIGHT
PEN IS DETERMINED. OTHERWISE, A RETURN WITH NO
INFORMATION IS MADE.
(OS) = DATA SEGMENT
(AH) = 0 IF NO LIGHT PEN INFORMATION IS AVAILABLE
aX,ex,ox ARE DESTROYED
(AH) = 1 IF LIGHT PEN IS AVAILABLE
(DH,DL) = ROW,COLUMN OF CURRENT LIGHT PEN
POSITION
(CH) = RASTER POSITION
(BX) = BEST GUESS AT PIXEL HORIZONTAL POSITION
ASSUME CS:ROMCODE,DS:DATA
;----- SUBTRACLTABLE
07CB VI LABEL BYTE
07CB 03 03 05 05 03 03 DB 3,3,5,5,3,3,3,4
03 04
0703 PROC NEAR
;----- WAIT FOR LIGHT PEN TO BE DEPRESSED
0703 B4 00
0705 SB 16 0063
0709 83 C2 06
07DC EC
0700 AS 04
07DF 75 7E
07E! AS 02
07E3 75 03
07E5 E9 OS69 R
07E8
07ES
B4 10
07EA
8B 16 0063
07EE SA C4
07FO
EE
07Fl
42
07F2
EC
07F3 8A E8
07F5 4A
07F6
FE C4
07F8
SA C4
07FA
EE
07FB
42
OlFC
EC
07FD SA E5
MOV
MOV
ADD
IN
TEST
JNZ
AH,O
OX, ADDR_6S45
DX,6
AL,DX
AL, LIGHLPEN_SWITCH
V6
NOW TEST FOR LIGHT PEN TRIGGER
TEST AL ,2
JNZ V7A
JMP V7
SET NO LIGHT PEN RETURN CODE
GET BASE ADDRESS OF 6S45
POINT TO STATUS REGISTER
GET STATUS REGISTER
TEST LI GHT PEN SWITCH
NOT SET, RETURN .
TEST LIGHT PEN TRIGGER
RETURN WIO RESETTING TRIGGER
TRIGGER HAS BEEN SET, READ THE VALUE IN
V7A:
MOV AH,16 ; LIGHT PEN REGISTERS ON 6845
INPUT REGS POINTED TO BY AH, AND CONVERT TO ROW COLUMN IN OX
MOV
DX,ADDR_6S45
ADDRESS REGISTER FOR 6845
MOV AL,AH REGISTER TO READ
OUT OX ,AL SET IT UP
INC DX DATA REGISTER
IN AL,DX GET THE VALUE
MOV CH,AL SAVE IN CX
DEC OX ADDRESS REGISTER
INC AH
MOV AL,AH SECOND DATA REGISTER
OUT DX,AL
INC OX POINT TO DATA REGISTER
IN AL,DX GET SECOND DATA VALUE
MOV AH,CH AX HAS INPUT VALUE
; ----- AX HAS THE VALUE READ IN FROM THE 6S45
2-108 ROM BIOS