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DPC31 HW

Page 56 Version V 1.0

DPC31 HW Description

7.5.2.3 Power-Saving Serial Interface

Figure 7.5-7 shows three different interfaces of the SIM1 at the DPC31.

If no galvanic isolation of the bus interface (SIM1) is required by the application-specific electronics, the send

signals (TxS, TxE) and receive signals (RxS, RxA) are passed on without processing in the DPC31 to the

synchronous bus physics unit (Figure 7.5-8a) with the parameter assignment GIM_EN=’0’ (Galvanic Isolation

Mode, refer to Param Register, Chapter 3.3) in the interface of the power-saving serial interface. The output

levels RxA and RxS are adjusted via the supply input V

(SIM1).

To galvanically isolate the lines for the data- and auxiliary signals, different isolated components and circuits

can be used (Figure 7.5-7b and c). The conventional type provides for an optocoupler each for the signals

TxS, TxE, RxS (and RxA). Otherwise, processing the send and receive signals in the interface of the power-

saving serial interface is as shown in Figure 7.5-7a.

To implement a power-saving method of working with optocouplers, an interface logic was conceived (Figure

7.5-7c) which is to be activated via the parameter assignment GIM_EN=’1’.

This circuit generates short pulse-width modulated transmission pulses only in the case of edge transitions of

the data stream from which the data signal is recovered in the secondary circuit.

The mean power input can thus be reduced to low values. The following are pointed out as special features:

• Combination of the control and data signals in a transmission channel (TxSD, RxSD); thus, reducing the

interface width for send and receive direction from 4 to 2 optocoupler channels.

• Suitable for 5V and 3V engineering

• Use of conventional optocoupler blocks with simple selection at the manufacturer; can also be used for

optocouplers with higher power requirements and approval for intrinsically safe circuits.

•

The power-saving interface can be used only for a transmission rate of 31.25kBd (refer to Param

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Siemens SPC3 Specifiche Pagina 58