Stahl PROFIBUS DP Series, Руководство по эксплуатации

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Operating Instructions
IS1 PROFIBUS 3.00 E - Technical alterations reserved -
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PROFIBUS DP interface for IS1+
Function:
- The switchover criterion between primary and backup CPU is generated in the IS1 CPUs. No support from
control commands by the DP master is required.
- Our GSE versions 2.xx support DP master systems which do not yet support DPV1 diagnoses.
- A failure of the backup CPU
is reported via the “Backup Slave Not Available” device-specific diagnosis as
well as the CPU status register in the cyclic data of the primary CPU.
- From the point of view of the DP masters, the slave (IS1 CPU) will fail for a short period during a switchover
between the primary and backup CPU and return to the Data_Exchange after approx. 500 ms - 800 ms
using 1,5 MBaud (see table in chapter
Project planning ).
During the switchover of IS1, output signals are frozen are thus bumpless. The maximum allowed switch
over time can be set by the parameter ´timeout output modules´.
For bumpless switchover of the input signals, the only additional support required by the DP master is a
toleration of such a short-term slave failure. Input signals and the signal and device status must be
frozen during this DP master switchover time. Thus, the short slave failure is hidden from the application
software in AS. If possible, the slave failure time tolerated by the DP master should be configurable. If a
slave fails for more than the configured slave failure time, the appropriate safety reaction can take place
in the AS.
- For standard DP masters which do not tolerate such a short slave failure, the application software will see
this short slave failure in the AS.
With some systems and suitable design of the application software, such a bump can be tolerable. This
must be checked in each individual project.
- Optionally, the bumpless switchover of input signals can be effected on the application level in the
AS for each specific project.
For example, input signals can be copied from the DP master input/output image to a second memory
area the remaining application software has access to. In this case, during the slave switchover phase,
transfer between these two memory images is prevented, thus freezing the memory area of the
application. The behavior of the system messages in the AS must also be taken into account.
For function-block-based systems, it is possible, for example, to insert a proprietary block, which carries
out a bumpless switchover, for each input signal.
AI or DI FB
Proprietary project specific.
Function Block
Application software FBs
Status without bump Status with bump