PCM-MIO-A-1/Software Summary
v1.0
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Page 19
8.1.3 Command Register
Each A/D device contains an 8-bit command register to configure the
inputs as single-ended or differential with a desired input range of 0 V–5 V,
0 V–10 V, ±5 V, and ±10 V. The following describes the register options.
8.1.4 Multiplexer Channel Selection
Channel Selection
Bits 7
–
4 of the command register assigns the channel configuration for the
requested conversion. The converter measures the voltage between the
two channels indicated by the + and - signs in the table below. In
differential mode, measurements are from any of the four adjacent input
pairs in either polarity. In single-ended mode, all input channels are
measured with respect to GND. Both the + and - inputs are sampled
simultaneously so common mode noise is rejected.
Range Selection
Bits 3 and 2 of the command register determine the input range for the
conversion. Setting UNI to a logical one selects a unipolar conversion while
a zero selects bipolar. The GAIN bit selects the input span for the
conversion in conjunction with the UNI bit. The table below defined the
selection options.
INPUT RANGE
7
6
5
4
3
2
1
0
SGL / DIFF ODD SIGN SELECT 1 SELECT 0
UNI
GAIN
NAP
SLEEP
MUX CHANNEL SELECTION
NOT SUPPORTED
MUX ADDRESS
DIFFERENTIAL CHANNEL SELECTION
MUX ADDRESS
SINGLE-ENDED CHANNEL SELECTION
SGL/
DIFF
ODD
SIGN
SELECT
0
1
2
3
4
5
6
7
SGL/
DIFF
ODD
SIGN
SELECT
0
1
2
3
4
5
6
7
COM
1
0
1
0
0
0
0
0
+
-
1
0
0
0
+
-
0
0
0
1
+
-
1
0
0
1
+
-
0
0
1
0
+
-
1
0
1
0
+
-
0
0
1
1
+
-
1
0
1
0
+
-
0
1
0
0
-
+
1
1
0
0
+
-
0
1
0
1
-
+
1
1
0
1
+
-
0
1
1
0
-
+
1
1
1
0
+
-
0
1
1
1
-
+
1
1
1
1
+
-
