IBM XT 5160 Technical Reference page 312

; ----- AX HAS THE VALUE READ I N FROM THE 6845
;----- TRIGGER HAS BEEN SET, READ THE VALUE IN
5-165
SECOND DATA REG I STER
IF POSITIVE, DETERMINE MODE
<0 PLAYS AS 0
DETERM I NE MODE
SET - 8 SHIFT COUNT
DE TERM I NE I F GRAPH I CS OR ALPHA
ALPHA_PEN
ALPHA_PEN
SAVE ROW VALUE IN CH
-2 FOR EVEN/ODD FIELD
COLUMN VALUE TO BX
MUL TI PL Y BY 8 FOR MED I UM RES
DETERM I NE MED I UM OR HIGH RES
NOT HIGH RES
SHIFT VALUE FOR HIGH RES
COLUMN VALUE TIMES 2 FOR HIGH RES
NOT HIGH RES
MULTIPLY--16 FOR HIGH RES
TE ST LI GHT PEN TR I GGER
RETURN WITHOUT RESETT I NG TR I GGER
POINT TO DATA REGISTER
GET SECOND DATA VALUE
AX HAS INPUT VALUE
ADDRESS REG I STER FOR 6845
REG I STER TO READ
SET IT UP
DATA REGISTER
GET THE VALUE
SAVE IN CX
ADDRESS REG I STER
SET NO LIGHT PEN RETURN CODE
GET BASE ADDRESS OF 6845
PO I NT TO STATUS REG I STER
GET STATUS REG I STER
TEST LIGHT PEN SWITCH
NOT SET, RETURN
DIVISOR FOR GRAPHICS
DE TERM I NE ROW ( AL ) AND COLUMN ( AH)
AL RANGE 0-99, AH RANGE 0-39
; LIGHT PEN REGI STERS ON 6845
; SET UP COUNT FOR BEEP
; SOUND THE POD BELL
; TTY_RETURN
; MODE VALUE TO BX
; DETERM I NE AMOUNT TO SUBTRACT
; TAKE I T AWAY
NEAR
AL,2
V7A
V7
AH,16
CL,3
CRT MODE,4
V4 -
CRT MODE,7
V4 -
BL,CRT MODE
BH,BH -
BL,CS:VI [BX]
AX,BX
BX,CRT START
BX,I -
AX,BX
V2
AX,AX
PROC
DL,40
DL
DX, ADDR 6845
AL,AH -
DX,AL
DX
AL,DX
CH,AL
DX
AH
AL,AH
DX,AL
DX
AL,DX
AH,CH
AH,O
DX, ADDR 6845
DX,6 -
AL,DX
AL,4
V6
BL,2
BEEP
U5
ENDP
(AH)
TEST
JNZ
JMP
MOV
CMP
JB
CMP
JE
MOV
SUB
MOV
SUB
MOV
SHR
SUB
JNS
SUB
MOV
MOV
MOV
OUT
INC
IN
MOV
DEC
INC
MOV
OUT
INC
IN
MOV
MOV
MOV
ADD
IN
TEST
JNZ
MOV
DIV
PC-XT System BIOS (11/08/82)
I NPUT REGS PO I NTED TO BY AH, AND CONVERT TO ROW COLUMN IN DX
ASSUME CS: CODE ,DS: DATA
SUBTRACT TABLE
LABEL -BYTE
DB 3 , 3 , 5 , 5 , 3 , 3 , 3 , 4
LIGHT PEN
TH I S ROUT I NE TESTS THE LIGHT PEN SW I TCH AND· THE LIGHT
PEN TR I GGER. I F BOTH ARE SET, THE LOCA T I ON OF THE LIGHT
PEN I S DETERM I NED. OTHERW I SE , A RETURN WITH NO
I NFORMAT I ON I S MADE.
ON EX I T
( AH )
=
0 I F NO LI GHT PEN I NFORMA T I ON I S AVA I LABLE
BX, CX, DX ARE DESTROYED
IF LI GHT PEN I S AVA I LABLE
( DH ,DL )
=
ROW, COLUMN OF CURRENT LIGHT PEN
POS ITION
(CH)
=
RASTER POSITION
(BX)
=
BEST GUESS AT PIXEL HORIZONTAL POSITION
;----- NOW TEST FOR LIGHT PEN TRIGGER
; ----- BELL FOUND
;----- GRAPHICS MODE
;----- DETERMINE MODE OF OPERATION
;----- DETERMINE GRAPHIC ROW POSITION
;----- WAIT FOR LIGHT PEN TO BE DEPRESSED
V7A:
MOV
CH,AL
ADD
CH,CH
MOV BL,AH
SUB BH,BH
CMP CRT_MODE,6
JNE V3
MOV
CL,4
SAL
AH,I
V3:
SHL
BX,CL
MOV
CALL
JMP
WR I TE_TTY
UII:
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988 V2:
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
500 I
5002
5003
5004
5005
5006
5007
5008
5009
5010
50 I I
5012
LINE SOURCE (B I OS FOR THE I BM PERSONAL COMPUTER XT) I I /08/82
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
LOC OBJECT
F7BI
F7BI B410
F7F5 8AE8
F7F7 02ED
F7F9 8ADC
F7FB 2AFF
F7FD 803E490006
F802 7504
F804 Bl04
F806 DOE4
F808
F808 D3E3
F7AA A802
F7AC 7503
F7AE E98100
F7El
F7El Bl03
F7E3 803E490004
F7E8 722A
F7EA 803E490007
F7EF 7423
F7C8 8A I E4900
F7CC 2AFF
F7CE 2E8A9F94F7
F7D3 2BC3
F7D5 8B 1E4EOO
F7D9 DIEB
F7DB 2BC3
F7DD 7902
F7DF 2BCO
F7B3 8B 166300
F7B7 8AC4
F7B9 EE
F7BA 42
F7BB EC
F7BC 8AE8
F7BE 4A
F7BF FEC4
F7C I 8AC4
F7C3 EE
F7C4 42
F7C5 EC
F7C6 8AE5
F78D
F78D B302
F78F E87602
F792 EBDB
F7Fl B228
F7F3 F6F2
F794
F794 03
F795 03
F796 05
F797 05
F798 03
F799 03
F79A 03
F79B 04
F79C
F79C B400
F79E 8B 166300
F7A? 83C206
F7A5 EC
F7A6 A804
F7A8 757E