Siemens S5-135U/155U appendix Measured-Value Representation with Various Ranges, Bit Significance

Analog Input/Output Modules

9.6.8Measured-Value Representation

Measured-Value Representation with Various Ranges

After conversion, the digital result is stored in the module's RAM. The bits in both bytes have the following significance:

				Byte 0										Byte 1
	7	6	5	4	3		2	1	0	7	6	5	4		3	2	1	0
12		11	2 10	2 9	2 8	2 7		2 6	2 5	2 4	2 3	2 2	2 1	2 0		A	E	OV
2		2
						Binary Value
Active Bit;				is not assigned
Error Bit;				is set in case of internal error;
				in this case, the measured value
				is not valid
Overflow Bit;				(is set if the range limit is reached)

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

OV Overflow bit

EError bit

A Active bit

Signal Status

1

1

0

Meaning of the

Signal Status

Range exceeded *

Broken wire

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:

SBit 7 in the high byte (212) indicates the sign for bipolar measured-value representation (two's complement and value with sign).

SBit 6 in the high byte (211) is not used in the case of bipolar measured-value representation (no overrange).

SThe 466 module has no overrange.

SSelective sampling is not possible with the 466 module (active bit is not set).

System Manual	9-91
C79000-G8576-C199-06