Siemens SIMATIC NET PROFIBUS Monitoring the Optical Link, Monitoring the Optical Receive Activity

6ZB5530–3AC30–0BA1 Infrared Link Modul (ILM)

5.6Monitoring the Optical Link

The PROFIBUS ILM has two mechanisms with which it monitors problems on the optical link.

–monitoring of the optical receive activity

–monitoring of the optical link with an acknowledgment pulse

5.6.1Monitoring the Optical Receive Activity

With the yellow “RX” LED, the PROFIBUS ILM indicates the reception of data via the optical channel of the PROFIBUS ILM. The pulse for the LED is extended to approximately 300 ms so that it is possible to recognize data reception even when small amounts of data are received.

Apart from the optical display using the “RX” LED, the PROFIBUS ILM also has integrated monitoring logic that triggers the signaling contact when problems occur receiving data on the optical channel provided the user configures this function with a switch. Problems in reception on the optical channel occur when there has been no change in the status of the optical receive channel for a period of approximately 300 ms, in other words when no message was received within 300 ms or a received message takes longer than 300 ms.

Note

The “activate signaling contact if problems occur in reception” configuration should not be set on the PROFIBUS ILM in the master subnet if its partner ILM only has one slave node that is not addressed during this time.

5.6.2Monitoring the Optical Link with an Acknowledgment Pulse

During configuration, the user can activate a mechanism so that an acknowledgment pulse is expected from the receiving station after data have been sent. This acknowledgment must be received within the time set as the interval between sending and transmitting on PROFIBUS (11 bit times). This acknowledgment pulse is not passed on to the electrical channels of the sending or receiving PROFIBUS ILM but is restricted exclusively to the optical transmission link.

Note

The “monitor link with acknowledgment pulse” configuration must be activated on both PROFIBUS ILMs of a point-to-point link.

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