Pepperl+Fuchs FieldConnex Segment Coupler 3 Manual page 30

PROFIBUS Power Hub Segment Coupler 3 (SK3)
PROFIBUS Commissioning
The T is usually entered via the configuration tool. The watchdog setting in the
WD
DP/PA gateway is transparent. In some configuration tools, the response monitor is preset once
for the PROFIBUS master. In other tools, the response monitor is preset individually for each
PROFIBUS PA participant. The response monitor value does not change in any way.
Many tools calculate the T
time of the master.
If the baud rates at the PROFIBUS DP end are high (e.g., 1.5 MB/s), the cycle times of the PA
end are up to 300 x longer. If a PROFIBUS PA device is directly programmed with a T
calculated at a higher master baud rate (DP), this is usually shorter than the PA cycle and the
device does not exchange data.
In order to ensure that the DP/PA gateway operates reliably, it is recommended that you set the
following bus parameters:
Program only one T
■
period in order to define the T
Program one T
■
The preset (programmed) time T
T . This is determined as follows:
V_max
The follwing 2 types of watchdogs can be configured on the HD2-GTR-4PA in cyclic or acyclic
data exchange, (see chapter 6.3.4:
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 from the DP side.
Note!
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
Information on 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:
with T
cycle_PA_channel
T = cycle time of PROFIBUS DP
cycle_DP
The PA cycle time T
Number of devices attached to the bus on 1 channel n
■
User data length L
■
The effective data length L is a unitless variable calculated as the sum of input and output
effective data quantity (in bytes) of all devices.
The following is an approximate calculation for the cycle time. 
For a nonredundant system: T
For a redundant system: T
30
automatically with a corresponding baud rate based on the cycle
WD
for the entire PROFIBUS system. Determine the longest delay
WD
.
WD
for each individual slave.
WD
must be greater than the maximum occurring delay period
WD
= T + T
Cycle_DP Cycle_PA_Channel
= cycle time of the PROFIBUS PA channel
depends on the following aspects:
cycle_PA_channel
Cycle_PA_channel
Cycle_PA_channel
TCycle_PA_Channel
= (0.256 ms * L) + (n * 12 ms) + 40 ms
= (0.256 ms * L) + (n * 12 ms) + 100 ms
WD
+ 500 ms