4 The PROFview XL Application Software User Manual PROFview XL
4.4.3.2 Illegal frames
The counter for illegal frames represents an online bus monitoring function. The PBT monitors each frame
transmitted on the connected PROFIBUS and checks it for protocol errors (for a detailed description of the il-
legal frames, see Section 3.3.3 "Illegal frames"). A maximum of 50,000 illegal frames is possible. If this num-
ber is exceeded, ">50,000" is displayed. Double-click on the illegal frames to reset their values to zero.
The value of the illegal frame counter can be recorded in a PBT document, like all measurement data. The
recording can be started and also be stopped by clicking with the left mouse button on the illegal frame icon
or by activating the option "Record online monitoring - illegal frames" in the "Configure segment" view. Any in-
crementing of the illegal frame counter from the time of activation is thus saved in the document and can later
be displayed and printed in the test log. The "REC" icon displays whether or not the recording is currently run-
ning (
) ( ).
It should be taken into account that the illegal frame counter is reset automatically after each change and af-
ter execution of the automatic baud rate detection. For correct frame detection and thus error analysis, it is
imperative that the baud rate is set correctly; otherwise, all traffic on the bus is detected as an error.
4.4.3.3 Bus cycle time
The determination of the bus cycle time – like the illegal frame counter – represents an online bus monitoring
function. With the baud rate set correctly and the PBT connected to a running PROFIBUS plant, the graphics
display the current, the minimum and the maximum bus cycle time since the start of the measurement, as
well as the master address. The number displayed to the left of the bar corresponds to the minimum mea-
sured time, and the number to the right of the bar to the maximum measured time. The master address from
which the token is currently being measured is specified in brackets after the current bus cycle time. During
the operation of the PBT master simulator, no bus cycle time is measured (display: "No token").
As already described in detail in Section 3.3.2 "Bus cycle time ", the bus cycle time is measured with a time
resolution of 100 µs and displayed as a value in microseconds. A value less than 100 µs results in "<0.1 ms"
being displayed. The longest time which can be measured is one second. If no token has been received from
the detected master for one second or if the PBT is connected to an idle plant, "No token" is displayed. In this
state, the PBT will automatically search for the first available token of a master and - after detection - will start
the determination of the minimum and maximum bus cycle times
7
.
Double-clicking with the mouse on the bus cycle time graphics will perform a reset resetting all memories
("Reset" is displayed). Subsequently, the PBT will wait again for the first available token from a master.
The data of the bus cycle time detection can also be recorded in a PBT document. Clicking with the left
mouse button on the bus cycle time icon or activating the "Record bus cycle time" option in the "Configure
segment" view will start recording of the measurement data. The "REC" icon displays whether or not the
recording is currently running (
) ( ).
It should be taken into account that - analogously to the illegal frame counter - changing the baud rate and
execution of the automatic baud rate detection results in resetting of the bus cycle time. The correct detection
of a token for displaying the bus cycle time requires the baud rate to be set correctly.
7 With multi-master systems, it is possible that, after a reset of the bus cycle time, a different master address is determined and dis-
played.
16 PROFview XL
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