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Figure 3-9 The WL diagnostic information is currently in the S7 diagnosis buffer. An incoming
diagnostic message is not present.
Data Exchange via DPV1
PROFIBUS-DPV1 (DPV1) is an
enhancement of the PROFIBUS-DP
protocol. PROFIBUS-DP and DPV1
devices can be connected to one
line. Being downwards compatible,
the PROFIBUS-DP and DPV1 protocol
can run on the same line. With DPV1,
additional data records with up
to 240 bytes of user data can be
transmitted acyclically by means
of user programs, such as STEP7,
or WinCC.
In this way, the DPV1 protocol can
be used to transmit parameter,
diagnostic, control, and test data
quickly and easily.
One prerequisite here is that a
DPV1-capable class 1 master or
class 2 master is available. These
can be used to transmit the above
data via an additional channel.
WL PROFIBUS Communication and Electronic Accessories • July 2004
With the class 2 master, a
communication link can even be
established to slaves that have not
been configured or parameterized
by this master and are still
connected to a class 1 master.
A class 2 master is particularly
suitable for commissioning,
diagnosis, and visualization tasks
with a program such as WinCC,
for example.
Special system functions that enable
data records to be sent and received
are available in SIMATIC S7 for
enhanced data transmission via
DPV1. The following example
illustrates how a data record is read
and written from the WL breaker.
System functions SFC58 (write)
and SFC59 (read) are used.
PROFIBUS Communication
WL Circuit Breaker
Note: The value specified for
parameter "IOID" depends on the
logical base address "LADDR." The
smaller input or output address,
which is displayed or was entered
under DP Slave Properties on the
"Address / ID" tab page, is always
used as the logical base address.
Depending on whether an input
or output address exists, the
ID's 'B#16#54' for the input and
'B#16#55' for the output are
specified for the 'IOID' parameter.
If the input and output addresses
are identical, the ID 'B#15#54' for
inputs is also parameterized.
For more information on the
system functions, refer to the
reference manual 'System
Software for S7-300/400 System
and Standard Functions.'
Cyclic (recurring) use of acyclic
services
If data is to be read via the C1
channel (DPV1 class 1 master) or
C2 channel (DPV1 class 2 master)
in a recurring time frame, the
minimum interval between two
read requests for each channel
must be 200ms.
Write requests via the C1 or C2
channel should generally be sent
on an event-controlled basis rather
than in a recurring time frame.
If these intervals are undershot,
resource problems can occur in
the communication interfaces,
which could, in turn, result in
communication on the C1 and/or
C2 channels being interrupted.
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