Specifications

Analog Input Modules
31007715 6/2008 189
Data
Word Structure
The first, third, fifth, seventh, ninth, eleventh, thirteenth, and fifteenth registers in the
module's input process image are the data words. Each register represents the input
current of a channel in the IEC data format. The data has 15-bit + sign resolution.
The bit structure in each data register is as follows:
All 16 bits in the register are significant. They allow you to represent analog input
currents with all the integer values in the range -32 768 to +32 767.
In the 0 to 20 mA operating range, the sign bit (bit 15) is always 0, indicating that
negative current values are not read.
The value 0 represents 0 mA or 4 mA, depending on the range selected. The value
32 000 represents 20 mA. Errors and warnings are reported at the following counts.
Note: Errors and warnings are based on count values, not physical values. The
current values in the table below are ideal values.
Error 4 to 20 mA Range (default) 0 to 20 mA Range
OCE (over current error) 20.38 mA
(32 767)
20.48 mA
(32 767)
OCW (over current warning) > 20 mA
(32 001)
>20mA
(32 001)
UCW (under current warning) < 4 mA
(-1)
<0.48mA
(767)
UCE (under current error) <= 3.62 mA
(-767)
0
(0)
BWE (broken wire error) <1 mA
(-767 is still displayed))
N/A
(N/A)
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
sign
8
0
STB ACI 1400 Data Register Format
12
3
4
5
6
7
910111213
14
15
2
2
2
1
2
0
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