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Entry type: FAQ, Entry ID: 23642062, Entry date: 09/21/2015

How do you parameterize the disconnected channels of the SM 338 and how many addresses does the module occupy in the IO area of the inputs?

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You must parameterize the disconnected channels of the SM 338 with the value "none" and the module occupies 16 bytes in the IO area of the inputs.

More information about parameterizing and addressing is available in the manual "SIMATIC S7-300 Automation System S7-300 Module Data" in Entry ID 8859629.

The module SM338 occupies 16 bytes in the IO area of the inputs.

  • Only the first 12 bytes of the interface are relevant for you as user.
  • The following 4 bytes in the input area are reserved and have no significance for the user. (You cannot change the inputs in the program).

On the SM 338 position decoder module you can connect up to three absolute encoders (SSI). You can evaluate and process the encoder values captured by the SM 338 in the user program.

All three encoder channels are preset to the value "13 bit". The SM 338 monitors the SSI channels, for wire break, for example, which means that disconnected channels on the SM 338 must be parameterized with the value "none" (Fig. 1). This parameterization switches off the encoder input.

Fig. 1

If you retain the "13 bit" presetting for the disconnected channels, the wire-break and signal monitor recognizes an error. This error is then reported as a diagnostics message and indicated by the SF LED.

Creation Environment
The screen in this FAQ response was created with STEP 7 V5.5 SP2.


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