5 MPI Communication
5.2 Network rules
The Handheld Unit (HHU) and the Handheld Terminal 6 (HT 6) have inte-
grated terminating resistors.
2. At least one termination must be supplied with a 5V voltage.
To this aim, an MPI connector with the terminating resistor enabled must be
connected to an enabled device. To this aim, the MPI connection on the MPI
board of the SINUMERIK 840Di can be used.
3. Stubs (feeding cable from the bus segment to the node) should be as short
as possible, i.e. < 5m. Stubs not used should be removed if possible.
If possible do not use stubs at all.
4. Each MPI node must be connected first to the bus and then be enabled.
When disconnecting the node, first disable the node. Then you can discon-
nect the node from the bus.
5. A maximum of 2 of the following components can be connected per bus
– Machine control panel (MCP)
– Handheld unit (HHU)
– Handheld Terminal 6 (HT 6)
6. Do not enable the bus terminating resistors at the distributor boxes of an
HHU or HT 6, since they are already integrated in the appropriate device.
7. Maximum cable lengths:
200m per bus segment
2,000m overall length with RS-485 repeater.
in the connector enabled
MPI network with terminating resistor
with OP 012 and
Siemens AG, 2003. All rights reserved
SINUMERIK 840Di Manual (HBI) – 06.03 Edition