09.2008 Communication / PROFIBUS
Siemens AG 6SE7087-6QX70 (Version AK)
SIMOVERT MASTERDRIVES Compendium Motion Control 8.2-87
Diagnosis of clock synchronization in MASTERDRIVES MC:
♦ B0043 = 1: Application is synchronous with bus clock
♦ r748.9: Should fluctuate between 65515 and 20
For other diagnostic parameters, see Section "Diagnosis and
troubleshooting"
The following time data help you to calculate the available bus bandwidth
(12 Mbit/s):
♦ 150-200 µs "Isochronous master cyclical share" per DP slave (cyclical
services class 1 master)
♦ Approx. 600 µs for "Isochronous master acyclical share"
(acyclical services class 1 master)
♦ Approx. 700 µs for max. one further active node
(class 2 master)
♦ 1000 µs computation time for CBP2, in parallel to acyclical services
DP cycle
Takt
Iso-master
acyclical
Takt
Cl.2 master
acyclical
CBP2 processing
Iso-master
cyclical
Fig. 8.2-27 Splitting of DP cycle on isochronous PROFIBUS
Two mandatory time conditions:
♦ "DP cycle" > "Isochronous master cyclical share" + 1000 µs
♦ "DP cycle" > "Isochronous master cyclical share" + "Isochronous
master acyclical share" + "Class 2 master"
The following supplementary conditions currently apply to clock
synchronization on the isochronous PROFIBUS:
♦ Transmission rate: 12 Mbit/s (performance afforded by lower
transmission rates is too low for drives)
♦ Maximum number of nodes: 31
♦ Maximum distance: 100 m
♦ For class 1 master only (isochronous master)
♦ A maximum of one other master (class 2, PG), ideally no other master
♦ No repeaters, no fiber optics (which cause varying deadtimes)
♦ The CBP2 must, of course, be inserted directly in the basic board (or
via an adapter board). No technology board may be installed between
the basic board and the CBP2.
Diagnosis
Times
Supplementary
conditions
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