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© Siemens AG 2006 All Rights Reserved
SINUMERIK 840D/810D Start-Up Guide (IADC) – 03/2006 Edition
Settings, MPI/BTSS
3.1 MPI network rules for SINUMERIK 840D
The following basic rules should be followed when installing a network.
1. The bus line must be terminated at both ends. To do this, activate the termi-
nating resistor in the MPI connector of the first and last node,and deactivate
the remaining terminating resistors.
Note
S Only two resistors are permissible.
S With HHU, bus terminating resistors are hard-wired into the device.
2. There must be at least 1 termination at the supply voltage. This occurs auto-
matically when the MPI connector with active terminating resistor is connec-
ted to a live device.
3. Spur lines (lead cables from the bus segment to the node) should be as
short as possible.
Note
Any spur lines that are not assigned should be removed if possible.
4. Each MPI node must be connected before being activated. When an MPI
node is disconnected, the connection must be deactivated before the con-
nector can be pulled out.
5. One or two HHU may be connected per bus segment. No bus terminators
may be connected to the distributor boxes of an HHU. If necessary, an inter-
mediate repeater can be used to connect more than one HHU to a bus seg-
ment.
6. The following cable lengths for the standard MPI without repeater must not
be exceeded:
MPI (187.5 kBaud): max. total cable length 1000 m
Note
Piggy-back connectors are not recommended for power connections.
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