6 calibration and test – Measurement Computing CIO-DAS16/M1/16 User Manual
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Table 5-5. 82C55 Registers
Configure 82C55
None. No read back on 82C55
BASE + 403
Port C Output
Port C Input
BASE + 402
Port B Output
Port B Input
BASE + 401
Port A Output
Port A Input of 82C55
BASE + 400
WRITE FUNCTION
READ FUNCTION
ADDRESS
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.
Table 5-6. 82C55 Configuration Coding
IN
IN
IN
IN
155
9B
1
1
1
1
OUT
IN
IN
IN
154
9A
0
1
1
1
IN
OUT
IN
IN
153
99
1
0
1
1
OUT
OUT
IN
IN
152
98
0
0
1
1
IN
IN
OUT
IN
147
93
1
1
0
1
OUT
IN
OUT
IN
146
92
0
1
0
1
IN
OUT
OUT
IN
145
91
1
0
0
1
OUT
OUT
OUT
IN
144
90
0
0
0
1
IN
IN
IN
OUT
139
8B
1
1
1
0
OUT
IN
IN
OUT
138
8A
0
1
1
0
IN
OUT
IN
OUT
137
89
1
0
1
0
OUT
OUT
IN
OUT
136
88
0
0
1
0
IN
IN
OUT
OUT
131
83
1
1
0
0
OUT
IN
OUT
OUT
130
82
0
1
0
0
IN
OUT
OUT
OUT
129
81
1
0
0
0
OUT
OUT
OUT
OUT
128
80
0
0
0
0
CL
B
CU
A
DEC
HEX
D0
D1
D3
D4
NOTE: D7 is always “1”. D6, D5, and D2 are always “0”.
6 CALIBRATION AND TEST
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
TM
, calibration routine.
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.
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