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The Master Mode – Commands, Sequence, Programming

4-2

SIMATIC NET AS-Interface – Introduction and Basic Information

C79000-G8976-C089/03

4.1 Master-Slave Principle

How the AS-Interface Operates

The AS-Interface operates on the master-slave principle. This means that the AS-i

master connected to the AS-i cable controls the data exchange with the slaves via

the interface to the AS-i cable.

The following diagram illustrates the two interfaces of the AS-i master CP.

S The process data and parameter assignment commands are transferred via the

interface between the master CPU and the master CP.

The user programs have suitable function calls and mechanisms available for

reading and writing via this interface.

S Information is exchanged with the AS-i slaves via the interface between the

master CP and AS-i cable.

PLC / PC

CPU

I/O

Configuration

Address

AS-i cable

AS-i slave

User

program

AS-i master

Interface to the user

program

Para-

meters

Figure 4-1

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Siemens SIMATIC Distributed I/O System DP/ASi Link Manual de Serviço Página 42