D
3--
02
D
A
2-
C
ha
nn
el
A
na
lo
g
O
utp
ut
6--7
D3--02DA 2-Channel Analog Output
R001
MSB
LSB
0
1
0
0
1
7
-- analog data bits
The first register contains the data for
channel one (R001). The second register
contains the data for channel two (R011).
Bit
Value
Bit
Value
0
1
4
16
1
2
5
32
2
4
6
64
3
8
7
128
Since the module has 8-bit resolution, the analog signal is converted into 256
“pieces” ranging from 0 -- 255 (2
8
). For example, with a 0 to 10V scale, a 0V signal
would be 0, and a 10V signal would be 255. This is equivalent to a a binary value of
0000 0000 to 1111 1111, or 00 to FF hexadecimal. The following diagram shows how
this relates to each signal range.
+10V
0V
0
255
0V -- 10V
20mA
4mA
0
255
4 -- 20mA
Each “piece” can also be expressed in
terms of the signal level by using the
equation shown. The following table
shows the smallest signal levels that will
result in a change in the data value for
each signal range.
Resolution
=
H
-
L
255
H = high limit of the signal range
L = low limit of the signal range
Range
Highest Signal
Lowest Signal
Smallest Change
0 to 10V
10V
0V
39 mV
4 to 20mA
20mA
4mA
62.5
µ
A
Now that you understand how the module and CPU work together to gather and
store the information, you’re ready to write the control program.
Analog Data Bits