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7.15 About initialization of AO/DO channels from user-defined values
Background
In Experion R410.1 or earlier, whenever there is a communication break, the output channels (AO/DO) would
either initialize to zero or hold the last value based on the type of the communication break. For example:
• PROFIBUS network is down - The outputs are initialized immediately to 0 in AO channels and to OFF in
DO channels. This is the default setting for almost all the slaves.
• Break in the FTE network
– If the Hold On Failure parameter is selected and there is an FTE communication break, the outputs hold
the last good value.
– If the Hold On Failure parameter is not selected, the outputs are initialized to zero, immediately in case
of an FTE communication break.
• During break in the slave communication (where Profibus network is up an running), DO/AO channels
initialized to 0 after communication break timeout expired.
This configuration is not desirable as all outputs initialize to zero and in turn this affects the process.
Overview
In Experion R410.2 and later, the DSBs are enhanced such that whenever there is a communication break within
the Profibus or in the FTE network, the output channels do not initialize back to zero immediately. Instead, the
output channels are initialized back from the user-defined values after recovering from the communication
break condition. However, the way in which the output channels initialize back from the user-defined values
differs based on communication break scenarios.
In Experion R430 and later, The GENPADSB and GENPAGWDSB are available for PA devices. GENPADSB
integrates PROFIBUS PA slave devices to Experion through transparent PA segment couplers. GENPAGWDSB
integrates PROFIBUS PA slave devices to Experion through non-transparent Profibus DP/PA link, namely
Siemens DP/PA link IM-157. Note that AO/DO initialization is supported when PA devices are disconnected
from the transparent gateway. However, AO/DO initialization is not supported when PA devices are
disconnected from the non-transparent gateway. AO/DO initialization is supported for the non-transparent
gateway when the Siemens DP/PA link IM-157 is disconnected.
Attention
This feature is not supported for the Siemens AS-i Link DSB.
The following table summarizes the various communication break scenarios and provides a description of how
the output channels initialize back from the user-defined values.
Scenario Output channel re-initialization description
• Profibus device is disconnected from the network.
• Profibus device has a power break condition and the
output channels are in an unpowered state.
The output channels are initialized back from the user-defined
values only after the connection breakout time timer has
exceeded.
FTE is removed If the Hold On Failure parameter is not selected, the channels
are initialized back from the user-defined values immediately.
The channels do not wait for the connection breakout time
timer.
7 DEVICE SUPPORT BLOCK (DSB)
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