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ADDRESS
BASE + 400
BASE + 401
BASE + 402
BASE + 403
The two groups of ports, group A and group B, may be independently programmed in one of several modes. The most
commonly used mode is mode 0, input / output mode. The codes for programming the 82C55 in this mode are shown
in Table 5-6 below.
D4
D3
0
0
0
0
0
0
0
0
0
1
0
1
0
1
0
1
1
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
NOTE: D7 is always "1". D6, D5, and D2 are always "0".
Every board is fully tested and calibrated before leaving the factory. For normal environments a calibration interval of
six months to one year is recommended. If frequent variations in temperature or humidity are common then
recalibrate at least once every three months. It takes less than 30 minutes to calibrate the board.
You will not need an extender card to calibrate theboard but you will need to have the cover off your computer with
the power on, so trim pots can be adjusted during calibration.
The A/D is calibrated by applying a known voltage to an analog input channel and adjusting trim pots for offset and
gain. There are two trim pots requiring adjustment to calibrate the analog input section. The entire procedure is
described in detail in the InstaCal
The CIO-DAS16/M1/16 should be calibrated for the range you intend to use it in. When the range is changed, slight
variations in zero and full scale may result. These variations can be measured and removed in software if necessary.
Table 5-5. 82C55 Registers
READ FUNCTION
Port A Input of 82C55
Port B Input
Port C Input
None. No read back on 82C55
Table 5-6. 82C55 Configuration Coding
D1
D0
HEX
0
0
80
0
1
81
1
0
82
1
1
83
0
0
88
0
1
89
1
0
8A
1
1
8B
0
0
90
0
1
91
1
0
92
1
1
93
0
0
98
0
1
99
1
0
9A
1
1
9B
TM
, calibration routine.
WRITE FUNCTION
Port A Output
Port B Output
Port C Output
Configure 82C55
DEC
A
128
OUT
129
OUT
130
OUT
131
OUT
136
OUT
137
OUT
138
OUT
139
OUT
144
IN
145
IN
146
IN
147
IN
152
IN
153
IN
154
IN
155
IN
6
CALIBRATION AND TEST
16
CU
B
CL
OUT
OUT
OUT
OUT
OUT
OUT
IN
OUT
OUT
IN
IN
OUT
OUT
IN
OUT
IN
IN
OUT
IN
IN
OUT
OUT
OUT
OUT
OUT
OUT
IN
OUT
OUT
IN
IN
OUT
OUT
IN
OUT
IN
IN
OUT
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
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