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Operation of The Card
Page 13
Blue Chip Technology Ltd.
01270146.doc
Page 13
Control Codes
The µPD71055 can operate in one of 3 modes.
The first (Mode 0) provides for simple inputs and outputs for three, 8 bit ports.
Data is written to or read from a specified port (A, B, or C) without the use of
handshaking.
The following table gives a summary of the most commonly used ‘Control
Words’ which must be written to the control port to configure the µPD71055
I/O ports in Mode 0.
CONTROL
WORD
(hex)
CONTROL
WORD
(decimal)
SET ALL
of PORT
A as
SET ALL
of PORT
B as
SET HIGH
4 BITS of
C as
SET LOW
4 BITS of
C as
80
128
Output
Output
Output
Output
81
129
Output
Output
Output
Input
82
130
Output
Input
Output
Output
83
131
Output
Input
Output
Input
88
136
Output
Output
Input
Output
89
137
Output
Output
Input
Input
8A
138
Output
Input
Input
Output
8B
139
Output
Input
Input
Input
90
144
Input
Output
Output
Output
91
145
Input
Output
Output
Input
92
146
Input
Input
Output
Output
93
147
Input
Input
Output
Input
98
152
Input
Output
Input
Output
99
153
Input
Output
Input
Input
9A
154
Input
Input
Input
Output
9B
155
Input
Input
Input
Input
Mode 1 enables the transfer of data to or from a specified 8 bit port (A or B) in
conjunction with strobes or handshaking signals on port C.
In Mode 2, data is transferred via one bi-directional 8 bit port (A) with
handshaking (port C).
Refer to the µPD71055 or i8255 data sheet for full details of the settings and use
of Modes 1 and 2.
Summary of Contents for AOP-12D
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