Siemens SINUMERIK 840Di Manual page 138

5 MPI Communication
5.2 Network rules
Example
5-138
Notice
S
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.
Notice
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
segment:
– 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:
S
200m per bus segment
S
2,000m overall length with RS-485 repeater.
HT 6
MCP
ON
OFF
Distributor
box
OFF
Terminating resistor
ON
in the connector enabled
Terminating resistor
ON
integrated
Fig. 5-1 MPI network with terminating resistor
PCU 50
with OP 012 and
HMI Advanced
OFF
MPI bus
ON
 Siemens AG, 2003. All rights reserved
SINUMERIK 840Di Manual (HBI) – 06.03 Edition
06.03
SINUMERIK 840Di
PCU 50
MCI board