03.06
2.3 MPI/OPI network rules
2-29
© Siemens AG, 2006. All rights reserved
SINUMERIK 840D Configuring Manual NCU (PHD) – 03.06 Edition
2.3 MPI/OPI network rules
The following devices can be interconnected across the MPI bus:
NCU
PCU
HT 6
HHU
MSTT/MCP
The MPI interconnecting cables are available in different lengths.
When installing a network, observe the following basic rules:
1. The MPI connection can be routed from one user to the next by plugging the
MPI connector of the outgoing cable onto the MPI connector of the incoming
cable.
2. The bus line must be terminated at both ends. To do this, enable the termi-
nating resistor in the MPI connector of the first and last node and disable the
remaining terminating resistors (see Fig. 2-3).
Note
Only two inserted terminating resistors are permitted.
In the case of the HHU/HT 6, bus terminating resistors are permanently
integrated in the device.
3. At least 1 terminal must be supplied with 5 V.
This is done by connecting an MPI connector with the terminating resistor
connected to an energized device.
Note
The NCU must be located at the end of the connection.
4. Drop cables (feeder cable from bus segment to node) should be as short as
possible.
Note
Unused spurs must be removed.
5. Every MPI node must first be connected and then activated.
When disconnecting an MPI node, first deactivate the connection and then
remove the connector.
6. A maximum of two of the HHU and HT 6 components can be connected for
each bus segment.
Use
Network
installations
2 Connection Conditions
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