Nck/Plc Data Exchange; Effects On The Spl - Siemens Sinumerik 840D sl Function Manual

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7.4.13

NCK/PLC data exchange

Cyclic F_DP data transfer
After evaluating the machine data of the F_DP communication through the NCK
and PLC--F_DP layer and initializing the parameterized F_SENDDP and
F_RECVDP drivers, cyclic operation of both F_DP layers is started.
From this instant in time onwards, the NCK initiates an OB40 alarm on the PLC in
the set F_DP clock cycle (multiple of the IPO clock cycle, set via MD
$MN_SAFE_SRDP_IPO_TIME_RATIO). The basic program software on the PLC
side for F_DP communication is then run.
If, when attempting to issue an OB40 request to the PLC, it is identified that the
previous request has still not been executed, then no new request is issued in this
F_DP clock cycle. An OB40 request is only issued to the PLC, if the PLC has
enabled the interface, i.e. after acknowledging the previous request.
From the first unsuccessful attempt, attempts to issue a new OB40 request to the
PLC are no longer realized in the F_DP clock cycle but in the IPO clock cycle, so
that a communication error (timeout) does not occur as a result of the delay on the
side of the external F--CPU.
If an OB40 request from the PLC is not acknowledged up to a max. limit value of
500 ms limit, Alarm 27352 "F_DP: Communication error %1, Error %2" is output
and the configured stop response (Stop D/E) initiated. F_DP communication
processing is stopped. The F_RECVDP drivers output fail--safe values (0) as F net
data.
After the OB40 has been exited, the PLC returns to the level that was interrupted.
The input image on the PLC side is updated in DB18 after the end of the actual
OB1 cycle. This therefore ensures that the PLC--SPL always processes contiguous
input information from a time perspective.
7.4.14

Effects on the SPL

Using the F_DP communication has no effect on existing SPL programs with
reference to the interlocking logic in them. However, a conflict can occur when
assigning SPL inputs, if an SPL input is to be written to from several applications,
e.g. F_RECVDP and PROFIsafe.
The multiple assignment of an SPL input is identified, when booting -- across
applications -- and is displayed using Alarm 27099 "Double assignment in SPL
assignment MD %1[%2] -- MD %3[%4]".
The evaluation of the status signals of the SPL connections and changing the
system responses in the case of an error must, if necessary, be additionally
programmed in the SPL.
© Siemens AG 2015 All Rights Reserved
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) - - 10.2015 Edition
7.4 Safety- -related CPU- -CPU communication (F_DP communication)
Connecting Sensors/Actuators
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