Siemens SIMATIC NET PROFIBUS Owner's Manual page 98

Configuring Networks
Note
Since the formula includes the delays of all fiber-optic and RS-485 cables, the
"Consider Cable Configuration" check box must not be activated in the "Cables"
tab on the "Options" dialog.
Figure 3-7 "Bus Parameters/User-Defined" Dialog in STEP 7 (V5.0)
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PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000