Siemens SINUMERIK FM-NC Installation And Startup Manual page 36

3 Settings, MPI / OPI
3.1 MPI/OPI, network rules
3.1 MPI/OPI, network rules
3-36
The following basic rules must be observed with respect to network installa-
tions:
1. The bus line must be terminated at both ends. To do so, switch in the termi-
nating resistor in the MPI connector in the first and last nodes. Switch off all
other terminating resistors.
Note
S
Only two terminating resistors may be activated in the same line at one
time.
S
The terminating resistors of the bus are permanently installed in the HHU/
HPU.
2. At least 1 terminator must be supplied with 5V voltage. This is achieved by
connecting the MPI connector with a fitted active terminating resistor to a
device that is connected to the power supply.
Note
The NC must be positioned at the end of the line.
3. Spur lines (feeder cable from bus segment to node) should be as short as
possible.
Note
Unused spurs should be removed wherever possible.
4. Each MPI node must first be connected and then activated.
When disconnecting the MPI node first deactivate the connection and then
pull out the connector.
5. One HHU and one HPU or two HHUs or two HPUs can be connected to
each bus segment. No bus terminators may be inserted in the distribution
boxes of the HHU or HPU.
If necessary, more than one HHU/HPU can be connected to a network seg-
ment with repeaters.
6. The following cables lengths for MPI or OPI for standard use without re-
peater must not be exceeded:
MPI (187.5 kbaud): max. cable length in total: 1000 m
OPI (1.5 Mbaud): max. cable length in total: 200 m
SINUMERIK 840D Installation and Start-Up Guide (IAD) – 04.00 Edition
 Siemens AG 2000 All Rights Reserved
04.00
03.96