Information About I/O Cycle Time - Pepperl+Fuchs HD2-GTR-4PA Manual

PROFIBUS Commissioning
While on other tools, the response monitor is preset individually for each
PROFIBUS PA participant. The response monitor value does not chan-
ge in any way.
Many tools calculate the time T
baud rate based on the cycle time of the master.
If the baud rates at the PROFIBUS DP end are high (e.g. 12 MBd), the
cycle times of the PA end may be 300 times longer. If a PROFIBUS PA
device has been programmed directly with a time T
higher master baud rate (DP), this is usually shorter than the PA cycle
and the device does not exchange data.
The following bus parameters should be used to ensure the DP/PA ga-
teway operates reliably:
• only one watchdog time T
PROFIBUS system. The longest delay period must be determi-
ned in order to define T
• one watchdog time T
ve.
The preset (parameterized) time T
mum occurring delay period T
Two types of Watchdogs can be configured on the HD2-GTR-4PA in cy-
clic or acyclic data exchange (chapter "Watchdog Time in the DTM" on
page 48):
• Transparent Watchdog: The Watchdog time on the DP side is
the same as on the PA side (= default setting).
• Fixed Watchdog: A Watchdog time is set on the HD2-GTR-4PA
for the PA side that is different than the DP side.
The HD2-GTR-4PA measures the current cycle time of each PA segment
and generates a diagnostic message if the Watchdog time is too short.
Then the Watchdog time must be increased. The Gateway diagnostics
are based on the following formula: 2 x T
Note
5.2.3

Information about I/O Cycle Time

The overall I/O data cycle time from a DP master via HD2-GTR-4PA to
a PA slave can be approximated as follows:
T
Cycle_IO_Data
where:
T
Cycle_PA_Channel
T
Cycle_DP
Subject to reasonable modifications due to technical advances.
34
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P R O F I B U S P
WD
WD
= T + T
Cycle_DP
= Cycle time of the PROFIBUS PA channel
= Cycle time of the PROFIBUS DP
H S
O W E R U B
automatically with a corresponding
WD
is programmed for the entire
WD
is programmed for each individual sla-
must be greater than the maxi-
WD
.
V_max
Cycle_PA_Channel
Cycle_PA_Channel
C
E G M E N T O U P L E R
calculated at a
WD
+ 500 ms
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