Siemens ET 7Y Series Especificaciones descargar pdf (Pagina 143)

Functions of the IM 151-7 CPU

8-31

ET 200S IM 151-7 CPU Interface Module

A5E00058783-04

Sequence of the assignment of S7 connections

When the system is configured with STEP 7, parameter blocks are generated that

are read out when the module is initialized. Thus, the module operating system

reserves or assigns the corresponding S7 connections. This means, for example,

that an Operator Station cannot access a reserved S7 connection for PD

communication.

If the module (CPU) also has S7 connections that are not reserved, these are free

to be used as required. The assignment of these S7 connections is in the order in

which the requirements arises.

Example

If there is only one remaining free S7 connection on the CPU, you can connect a

PD to the bus. The PD is then able to communicate with the CPU. However, the

S7 connection is only assigned when the PD communicates with the CPU.

If you connect an OP to the bus at precisely the time when the PD is not

communicating, the OP builds up a connection to the CPU. However, because an

OP, unlike a PD, maintains a permanent communication connection, you will no

longer be able to establish a connection via the PD.

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Siemens ET 7Y Series Especificaciones Pagina 143