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Siemens
Desigo TRA Engineering, mounting and installation
CM111043en_09
Building Technologies
MS/TP networks
2016-02-22
The Desigo TRA devices communicate with up to 115,200 bps.
All devices must be set to the same speed. Otherwise, no communication is
possible.
APDU timeout and APDU segment timeout recommendation:
16 devices: 6 sec 32 devices: 10 sec.
Set Max Master for all devices.
Set router address to 0.
Set Max Info Frame to 50 in the router.
Set Max Info Frame to 10 in the DXRs (default).
In case of communication problems, the speed can be reduced via tool.
The "Set Baud rate" function in ABT is only supported by Desigo TRA devices.
If a third-party device stays at another speed, the whole MS/TP communication
may break down.
As Desigo TRA creates much bus traffic, the number of devices in an MS/TP
network must not exceed the following values:
Baud rate
9,600
19,200
38,400
76,800 115,200
Number of devices
Not recommended
Max. 32 Max. 32
- -
(Max. 16) (Max. 16)
Ignoring these values may cause communications to break down and block for
all participants in the MS/TP bus segment.
The electrical capacity of 256 devices cannot be used, although Desigo TRA
devices have 1/8 load interfaces (32 loads * 8 = 256).
As all Desigo TRA devices are operated as masters, the max. address range is
0...127.
Siemens does not assume any responsibility for correct operation of third-
party devices in conjunction with Desigo TRA. Test such devices before
using them in a project.
The maximum of 32 loads must not be exceeded when using third-party devices.
Check the manufacturer’s literature for network loading information.
For more than 32 loads use a repeater.
Max. 2 repeaters in series are admissible.
Max. length between two room automation stations
500 m / 1650 ft
Max length for stubs
30 m / 100 ft
Max. cable length of an MS/TP segment (including stubs)
1000 m / 3300 ft
Length can be extended using one or two repeaters.
Creating network sections using a repeater may also help
in case of communication problems.
It is also possible to span long distances using routers and BACnet/IP.
Two resistors 120 Ohm (5% ½ W)
b and –
at BOTH ends of the
network segment.
One PTC thermistor (TRF250-120)
between Reference ( ) and earth
at ONE
end of the network segment. This prevents the cable from being damaged by
high ground currents that may occur if the reference wire is accidentally
grounded to earth ground at a second location.
Before installing the PTC thermistor, use a DMM to insure that the reference
wire is not already connected to earth ground.
Grounding of the
shield
at ONE end of the network segment.
Network settings
Note!
Number of devices
Addressing
Third-party devices
Network distances
Bus terminating
resistors
