Synchronous Operation - Siemens SIMATIC S7-300 Reference Manual

Programmable logic controllers module data

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Special Signal modules

Synchronous Operation

The basics of synchronous operation are described in a separate manual.

Hardware requirements

For the synchronous operation of the SM 338, you require:

• CPU which supports clocked operation

• DP master which supports the equidistant bus cycle

• Slave interface (IM 153-x) which supports synchronous operation

Characteristics

Depending on the system parameterization, the SM 338 works in either

non-synchronous or synchronous mode.

In synchronous operation, the data exchange between DP master and SM 338 is

synchronous to the PROFIBUS DP cycle.

In synchronous operation all 16 bytes of the checkback interface are consistent.

If synchronicity is lost due to faults or failure or delay of Global Control (GC), the

SM 338 goes back into synchronous operation in the next cycle without error

If synchronicity is lost, the checkback interface is not updated.

Programmable Logic Controllers S7-300 Module Data

A5E00105505-03

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