Siemens Simatic M7-400 Reference Manual page 159

Ensuring a Wire Break Check Is Carried Out
To ensure that a wire break check is carried out, you require an external sensor
circuit using a resistor of 10 to 18 kW. The resistor should be connected parallel to
the contact and should be arranged as closely as possible to the sensor.
This additional resistor is not required in the following cases:
• If two-wire BEROs are used
• If you don't parameterize the "Wire Break" diagnosis
Setting the Input Delay for Channel Groups
You can only set the input delay for each group of channels. In other words, the
setting for channel 0 applies to inputs 0 to 7 and the setting for channel 8 applies to
inputs 8 to 15.
Note
The parameters that are entered for the remaining channels (1 to 7 and 9 to 15)
must be equal to the value 0 or 8, otherwise those channels will be reported as
being incorrectly parameterized.
Any hardware interrupts that have occurred in the meantime will be reported after
acknowledgement.
Optimum Signal Propagation Delay
You can achieve the fastest signal propagation delay with the following settings:
• Both channel groups are parameterized with an input delay of 0.1 ms
• All the diagnoses (load voltage error, wire break) are deactivated
• Diagnostic interrupt is not enabled
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Digital Modules
4-37