8 measured-value representation – Siemens S5-135U/155U User Manual
Page 473
9-91
System Manual
C79000-G8576-C199-06
9.6.8
Measured-Value Representation
After conversion, the digital result is stored in the module’s RAM.
The bits in both bytes have the following significance:
Byte 0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
2
12
2
2
2
2
2
2
2
2
2
2
2
2
11
10
9
5
7
3
1
8
4
6
2
0
A
E
OV
Byte 1
Binary Value
is not assigned
is set in case of internal error;
in this case, the measured value
is not valid
(is set if the range limit is reached)
Active Bit;
Error Bit;
Overflow Bit;
Figure 9-32
Digital Result Representation
Bits 0 to 2 in byte 1 have no influence on the measured value, they only give
information on measured-value representation. The following table describes
their significance in more detail.
Bit
Significance
Signal Status
Meaning of the
Signal Status
OV
Overflow bit
1
Range exceeded *
E
Error bit
1
Broken wire
A
Active bit
0
Not used
*
A measuring-point overflow does not affect the overflow bits of the other channels;
i.e. the measured values of unaffected channels are correct and can be evaluated.
Please note the following special features:
S
Bit 7 in the high byte (2
12
) indicates the sign for bipolar measured-value
representation (two’s complement and value with sign).
S
Bit 6 in the high byte (2
11
) is not used in the case of bipolar
measured-value representation (no overrange).
S
The 466 module has no overrange.
S
Selective sampling is not possible with the 466 module
(active bit is not set).
Measured-Value
Representation
with Various
Ranges
Analog Input/Output Modules