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The table below shows the control words for the 16 possible Mode 0 Port VO combinations. The control words
which set Port B as an input cannot be used on the 1200.
When bit 7 of $e PPI conrol word is set to 0, a write can be used to individually program the Port C lines.
SeUResel
Function
0 = active
D7
D6
D5
D4
D3
D2
D1
DO
set
Bit
Blt Sel
0 = s e l
Blt Set/Reset
0 = s e l b i t t o 0
1 = s e t b i t t o l
Bit Select
000 = PCo
001 = Pc1
010 = PC2
0 1 1 = P C 3
100 = Pc4
101 = PC5
1 1 0 = P C 6
1 1 1 = P C 7
8255 Port l/O Flow Direction and ControlWords, Mode 0
Group A
Group B
ControlWord
Port A
Port C
Upper
Port B
Port C
Lower
Binary
Decimal
Hex
Output
Output
Output
Output
1 0 0 0 0 0 0 0
128
80
Output
Output
Output
Input
1 0 0 0 0 0 0 1
129
8 1
Output
Output
Input
Output
1 0 0 0 0 0 1 0
1 3 0
82
Output
Output
Input
Input
1 0 0 0 0 0 1 1
1 3 1
83
Output
Input
Output
Output
1 0 0 0 1 0 0 0
1 3 6
88
Output
Input
Output
Input
1 0 0 0 1 0 0 1
137
89
Output
lnput
Input
Output
1 0 0 0 1 0 1 0
1 3 8
8A
Output
Input
Input
lnpul
1 0 0 0 1 0 1 1
1 3 9
8B
Input
Output
Output
Output
1 0 0 1 0 0 0 0
144
90
Inpul
Output
Output
Input
1 0 0 1 0 0 0 1
1 4 5
9 1
Input
Output
Inpul
Output
1 0 0 1 0 0 1 0
1 4 6
92
Input
Output
Input
Input
1 0 0 1 0 0 1 1
147
93
lnput
Input
Output
Output
1 0 0 1 1 0 0 0
152
98
Input
lnput
Outpul
lnput
1 0 0 1 1 0 0 1
1 5 3
99
lnput
Input
Input
Output
1 0 0 1 1 0 1 0
1 5 4
9A
Input
Input
lnput
Input
1 0 0 1 1 0 1 1
1 5 5
9B
4-6
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