Table 6-31 Content Of The 4 Bytes Of Additional Ob40 Information During Hardware Or End Of Cycle Interrupts - Siemens SIMATIC S7-300 Manual
Automation system, module data
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Cycle time extension due to wire-break monitoring
The wire-break monitoring software function of the module is available in all operating
modes.
The 8-channel mode (hardware or software filter modes) extends module cycle times by 4
ms, irrespective of the number of channels at which wire-break monitoring is enabled.
In 4-channel mode (hardware filter), the module interrupts processing of input data for the
duration of 170 ms to perform a wire-break check, i.e. each wire-break check extends the
module cylce time by 93 ms.
Unused channels
For unused channels, set the "disabled" instruction at the "measuring method" parameter.
This reduces the module's cycle time.
You need to terminate any non-switched channels in an enabled group, i.e. you short circuit
the positive input and negative input of that channel.
This action enables you to achieve the following outcome:
● this prevents measurement errors on the channels used within a group
● Diagnosis messages from the unused channel in a group are suppressed
Short-circuit to M or L
If you short-circuit an input channel to M or L, the module does not suffer any damage. The
channel continues to output valid data and does not report a diagnostics event.
Special features of channel groups with respect to hardware interrupts upon limit violation
You can set the high and low limits triggering hardware interrupts separately for each
channel in
End of cycle interrupt
You can synchronize a process with the conversion cycle of the module by enabling the end
of cycle interrupt. The interrupt occurs when the conversion of all the enabled channels is
complete.
Table 6-31
Content of the 4 bytes of additional OB40 information during hardware or end of cycle interrupts
Content of the 4 bytes of additional information
Special
2 bits per channel to identify the range
analog
High limit exceeded at channel
flags
Low limit exceeded at channel
End of cycle event
Free byte
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
6.10 Analog input module SM 331; AI 8 x TC; (6ES7331-7PF11-0AB0)
STEP 7
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2
7
7
7
2
2
2
2
6
5
4
6
5
4
3
6
5
4
3
Analog modules
2
2
2
3
2
1
0
2
1
0
2
1
0
X
Byte
0
1
2
3
6-99
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Troubleshooting
