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Signaling Errors and Diagnostics in the User Program

4-2

SIMATIC NET CP 243-2 AS-i Master

C79000-G8976-C142/02

4.1 Signaling

Error Signaling

If the CP 243-2 recognizes errors on the AS-Interface (AS-i slave failure, AS-i

Power Failure) during operation, it signals these errors by resetting the input data

of the affected slave and by setting the corresponding bit in the error register in the

SM area (Special Memory).

The SM byte addresses depend on the slot of the CP 243-2.

Caution

Note that the operating system of the S7-200 CPU does not always update the

error register in the SM area before a program cycle. For this reason, it is possible

that the input data of a binary AS-i slave are set to ’0’ although no error is signaled

in the error register.

If you require a consistent view of the input data, error bits and the delta list for

programming your system, you can achieve this using the “Read Data and Delta

List” command (see Section 5.2.32).

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Siemens SIMATIC NET Manuale di Servizio Pagina 66