User Manual

Siemens Building Technologies PROFIBUS DP/P-bus link

Building Automation User's guide 5-7

5.4 Interconnection

The P-bus connection of the link incorporates an internal DC power supply for 128 load units, to

supply the power for the DESIGO I/O modules. The DESIGO I/O modules are connected via the

P-bus connection using the P-bus coupling module (I/O bar type PTX 1.01). The main supply

voltage is derived from a separate AC 24 V transformer.

As described in data sheets CM2M8102 and CM2N8022. a double-insulated safety transformer

to EN 61 558, designed for continuous operation, must be used. At least conductor G must be

fused. The transformer must be sized for the effective load of the equipment in the control panel

including the connected field devices.

For separate control panel construction, please observe grounding precautions (as described in

CM2M8102).

To avoid earth loops, only G0 must be earthed to a central point. The earthing precautions for

the P-bus must be observed

(see data sheets CM2M8102 and CM2N8022).

For load distribution purposes, the G0 connection of the P-bus coupling module (I/O bar, type

PTX1.01) must be connected to G0 of the transformer. The G0 connection (between PU and

PC) of the DP/P-bus link is designed for connection of the P-bus/remote bus. The remote bus

has not yet been released.

230V~

P-bus

coupling

module

PTX1.01

DP/ P-bus link

Profibus

(9-pin DSUB, RS485)

Ground

G G0 PU G0 PC PD

24V~

* Parallel connection of G0

(Terminal 2)

for connection of remote bus

not yet released.

Fig. 5-5: Overview of connections