IBM 5170 Technical Reference page 284

;----- WAIT FOR liGHT PEN TO BE DEPRESSED
070F B4 00
MOV
AH,O
SET NO liGHT PEN RETURN CODE
07E1 8B 16 0063 R
MOV
DX,ADDR 6845 GET BASE ADDRESS OF 6845
07E5 83 C2 06
ADD
DX,6 -
POINT TO STATUS REGISTER
07E8 EC IN Al, ox
GET STATUS REG I STER
07E9 A8 04 TEST Al,4
TEST liGHT PEN SW ITCH
OnB
74 03
JZ v6_A GO I F YES
07EO E9 0872 R
JMP V6 NOT SET, RETURN
;----- NOW TEST FOR liGHT PEN TRIGGER
07FO A8 02 V6_A: TEST Al,2 TEST liGHT PEN TRIGGER
07F2 75 03
JNZ
V7A RETURN WITHOUT RESETTING TRIGGER
07F4 E9 081C R
JMP
V7
; ----­ TR I GGER HAS BEEN SET. READ THE VALUE IN
07F7
V7A:
07F7 B4 10
MOV ; liGHT PEN REGISTERS ON 6845
I N PUT REGS PO I NTED TO BY AH, AND CONVERT TO ROW COLUMN I N OX
07F9
07FD
8B
8A
16
C4
0063 R
MOV
MOV
OX, AD DR 6845
Al,AH -
ADDRESS REGISTER FOR 6845
REG I STER TO READ
07FF
0800
EE
EB 00
OUT
JMP
DX,Al
SHORT $+2
SET IT UP
fa DELAY
0802 42 INC
OX
DATA REG I STER
0803
0804
0806
EC
8A
4A
E8
IN
MOV
DEC
Al,DX
CH,Al
OX
GET THE VALUE
SAVE IN CX
ADDRESS REG I STER
0807 FE C4
INC
AH
0809 8A C4
MOV
Al.AH SEGOND DATA REG I STER
080B EE
OUT DX,Al
080C 42 INC OX POINT TO DATA REGISTER
0800 EB 00
JMP
SHORT $+2
10 DELAY
080F EC
1 N AL, DX GET SECOND DATA VALUE
0810 8A,. E5
MOV
AH, CH AX HAS INPUT VALUE
; ----- AX HAS THE VALUE READ I N FROM THE 6845
0812 8A 1E 0049 R
MOV
BL, CRT MODE
0816 2A FF
SUB
BH, BH -
MODE VALUE TO BX
0818 2E: SA 9F 0107 R
MOV
BL,CS:Vl[BX] DETERM I NE A/-:OUNT TO SUBTRACT
0810 2B C3
SUB AX,BX TAKE I T AWAY
081F 8[3 lE 004E R
MOV
BX, CRT START
0823 01 EB SHR
BX,l ­
0825 2B C3
SUB
AX,BX CONVERT TO COI'(RECT PAGE ORIGIN
0827 79 02
JNS V2 IF POSITIVE, DETERMINE MODE
0829 28 CO
SUB AX,AX <0 PLAYS AS 0
;----- DETERMINE MODE OF OPERATION
082B V2:
DETERM I NE_MODE
082B Bl 03
MOV Cl,3 SET *8 SH I FT COUNT
0820 80 3E 0049 R 04
CMP
CRT_MODE,4 DETERM I NE I F GRAPH I CS OR ALPHA
0832 72 2A
JB VU ALPHA_PEN
0834 80 3E 0049 R 07
eMP
CRT_MODE,7
0839 74 23 JE VU ALPHA_PEN
;----- GRAPHICS MODE
083B B2 28
MOV
Dl,40 DIVISOR FOR GRAPHICS
0830 F6 F2 DIV OL
DETERMINE ROW(AL) AND COlUMN(AH)
Al RANGE 0-99, AH RANGE 0-39
;----- DETERMINE GRAPHIC ROW POSITION
083F 8A E8
MOV
CH,Al SAVE ROW VALUE INCH
0841 02 EO
AOO
CH, Cli *2 FOR EVEN/ODD FIELD
0843 8A DC
MOV
Bl,AH
COLUMN VALUE TO BX
0845 2A FF SUB BH, BH
MULTIPLY BY 8 FOR MEDIUM RES
0847 80 3E 0049 R 06 eMP CRT_MOOE,6
DETERMINE MEDIUM OR HIGH RES
084C 75 04 JNE V3
NOT HIGH RES
084E B1 04
MOV
Cl,4
SHifT VALUE FOR HIGH RES
0850 DO E4 SAL AH,l COLUMN VAlU E TIMES 2 FOR HIGH RES
0852 V3: NOT_H I GH~RES
0852 03 E3 SHl BX,Cl
Ml,ILTIPlY *16 fOR HIGH RES
;----- DETERMINE ALPHA CHAR POSITION
0854 8A DI~
MOV
Dl,AH COLUMN VALUE FOR RETURN
0856 8A FO
MOV
DH,Al ROW VALUE
0858 DO EE SHR DH,l
DIVIDE BY 4
085A DO EE SHR
DH,l FOR VALUE IN 0-24 RANGE
085C EB 12
JMP
SHORT V5
LI GHT_PEN_RETURN_SET
;----- ALPHA MODE ON LIGHT PEN
085E V4:
ALPHA_PEN
085E F6 36 004A R
OIV BYTE PTR CRT_COlS DETERM I NE ROW, COLUMN VALUE
0862 8A FO
MOV
DH,Al ROWS TO OH
0864 8A 04 MOV DL,AH COlS TO Dl
0866 02 EO
SAL
AL,Cl MULTI PLY ROWS * 8
0868 8A E8
MOV
CH,Al GET RASTER VALUE TO RETURN REG
086A 8A DC MOV
Bl,AH COLUMN VALUE
086C 32 FF XOR BH, BH
TO BX
086E 03 E3
SAL
BX,CL
0870 V5:
LIGHT PEN RETURN SET
0870 B4 01 MOV AH,1
t NO I CATE EVERTH I NG SET
0872
V6:
LIGHT PEN RETURN
0872 52 PUSH OX SAVE "RETURN VALUE (IN CASE)
0873 8B 16 0063 R MOV OX, AODR_6845
GET BASE ADDRESS
0877 83 C2 01 ADD
DX,7 POINT TO RESET PARM
oe7A EE OUT DX,AL
ADDRESS, NOT DATA, IS IMPORTANT
087B 5A
POP
ox
RECOVER VALUE
087C V1:
RETURN_NO_RESET
087C 50
POP BP
0870 SF POP 01
087E 5E POP SI
087F 1 F POP OS DISCARD SAVED BX, CX, OX
0880 1 F POP OS
0881 1 F POP
OS
0882 1 F
POP OS
0883 07
POP
ES
0884 CF I RET
0885
ENDP
0885
~~~~_LPE~NDS
END
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