What is needed, is to read in Port C and test the condition of D
5
for knowing the status of IBF
A
.
Test the condition of D
1
for the status of OBF
B
IN AL,PORTC ;read in the contents of Port C
TEST AL,5 ;for testing the condition of D
5
, IFB
A
TEST AL,1 ;for testing the condition of D
1
, OFB
B
PC
4, 5
PORT A – (STROBED OUTPUT)
PORT B – (STROBED INPUT)
RD
8
8
1=INPUT
0=OUTPUT
PA7–PA0
PC
7
PC
6
PC
3
PC
4, 5
PB7–PB0
PC
2
PC
1
PC
0
WR
CONTROL WORD
11011/001
D7
D6
D5
D4
D3
D2
D1
D0
INTR
A
I/O
INTR
B
IBF
B
STB
B
OBF
A
ACK
A
Figure 9.16 | Port A in strobed output ...
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