, 8255 , , /. 8255 , , 7 . 1, ; 7=0, / . 3-1 , 0 . .
, -. , 4 , - 4 . (0, 1, 2), - (0 1). , . 9.22.
. 9.21. 8255
0. . 4 , - . , . D4, D3, D1 DO , , - . :
. 9 22. 8255
D4 A
D3 ,
D1 - ,
DO -
0, ,
1. A, D4 (D4 = 1 ), .
:
4 STBA - 0 7- "" .
5 IFA , . 1, , . 0, .
6, 7 - . D3 0, ; - .
:
4, 5 - , 6, 7 .
7 FA - , . 0 , .
6 A - 0 , .
1 , INTRA. IR . 1, (. . 4), 0, . INTRA 1, , 0, . 1, D1 (D1 = 1 ). 2 1 STBB IBFB; , STBA IFA . 1 2 OBFB B. 0 INTRB INTRA. 4 6 . , 4 4 /. / 2.
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|
2. , . 2 , 4 :
4 STBA 0 7- .
5 IFA - 1, 1 7-, 0, .
6 A - , 7-.
PC7 OBFA 0, A , 0, .
py 2, pe 0 1. 0 2 - C0 , PC3 A. A 2, 2 C0 , A. B.
7- IN.
9 2.2
. 9.23 8255 - - . - , . 1. 7, . . (S/H) , . , , , . SA (4) 8255. . - 0; - . .
, , FFF8, FFF9 FFFA FFFB.
MOV AL, 10110000
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OUT DX, AL
1, - 0, 7 . - .
MOV DX, OFFFBH
MOV AL, 00001111B
OUT DX, AL
MOV AL, 00001110B
OUT DX, AL
DX , /, co PC7 = 1, - 7 = 0.
MOV DX.OFFFAH
AGAIN; IN AL,DX
TEST AL.,001OOOOOB
JZ AGAIN
MOV DX. OFFF8H
IN AL, DX
. 9.23. - - 8255
AL - .
MOV DX, OFFF9H
OUT DX, AL
, - , .
, . , .
, . "--", :
MOV CX, N
IDLE NOP
LOOP IDLE
. - . 9.24
- - , - , . , .
9.23 8- , 1 256. -10... +10 ,
20/256= 0,078.
10-, 12- 14- . 8255.