Application Examples; Interface Logic; Overview Of The Interface To The Communication Controller - Siemens ASIC SIM 1-2 Function Manual

Application Examples

4.1

Interface Logic

4.1.1

Overview of the Interface to the Communication Controller

The interface logic forms the interface to the communication controller of the user
electronics. As shown in the following diagram, three modes are possible.
● Without galvanic isolation
If galvanic isolation of the bus interface (SIM1-2) from the application-specific
electronics is not required, the send or received signals are passed on without
any processing and switched through to the user electronics. (Figure a). The
output level of RxA and RxS is adapted over the output voltage VREG as
reference voltage.
● Conventional isolation with optocouplers
To achieve galvanic isolation of the lines for data and associated signals,
various isolating components and circuits can be used. The conventional
method is a separate optocoupler each for the signals TxS, TxE, RxS and RxA
(Figure b).
● Power-saving isolation
With the power-saving galvanic isolation, only two optocouplers are necessary,
the data is then transferred using pulse duration modulated signals in the
galvanic isolation mode (Figure c). The Galvanic Isolation Mode (GIM) is
enabled with GIM = H.
The send and receive functions are implemented separately so that if the
physical characteristics of the bus are correct, the frame sent over TXS can be
received over RXS. The following two sections explain this circuit in more
detail.
SIM 1-2
C79000-G8976-C215-01
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