User Manual

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Siemens TX-I/O Engineering and installation guide CM110562en_13
Building Technologies Principles of electrical design 2019-05-15
10.3 Admissible number of devices
• Parallel operation: max. 4 power supply units per I/O island.
• Parallel operation: max. 2 power supply units per I/O row
Reason: max. current in the I/O row in case of a short-circuit.
• Island bus expansion: for each decentralized sub-island again up to 4 parallel power
supply modules, with up to 2 for each I/O row.
An external power supply is connected via a TXS1.EF10 bus connection module.
• No parallel operation admitted
• Separate fuse for each TXS1.EF10 bus connection module: max.6 A.
• Max. 16 bus connection points, e.g. 1 bus interface module + 3 supply modules
+ 12 bus connection modules)
Reason: with more bus participants, bus communications do not work anymore
 This means that the number of I/O rows in an I/O island is limited to 16.
• Max. length of one I/O row: 1.6 m (equivalent to 25 I/O modules, 512 data points)
Reason: To avoid a drop in the field supply voltage owing to the contact resistance at
the bus connectors.
• The maximum number of subscribers on the island bus is 64.
Reason: performance of the island bus.
This can be achieved, by a maximum of 16 rows of 4 modules, for example,
or by four rows of 16 modules.
Number of decentralized sub-islands per I/O island
Max. 8
Number of island bus expansion modules per
decentralized sub-island
Exactly 1
Number of I/O modules per I/O island
Maximum of 64
Number of I/O modules per sub-island No limit, as long as the
total of the entire island
(64) is maintained.
See PROFINET BIM User's manual [9]
Module power supply
TXS1.12F10 or
TXB1.PBUS or PXC3...
Module p
ower supply
3rd-party device DC 24 V
Bus connection modules
I/O row
I/O island
Limit
s for island bus
expansion
Limits in Simatic