Siemens SINUMERIK 840D sl Function Manual page 227

The monitoring time is set using MD $MN_SAFE_SDP_TIMEOUT[0...m].
When the monitoring time is exceeded, then depending on the system variables
$A_FSDP_ERR_REAC, the selected alarm responses are initiated:
Alarm 27350 "F_DP: %1 communication, DP_DP_ID = 52 signals error %3" and
Alarm 27351 "F_DP: %1 communication, DP_DP_ID = 52 signals error %3".
Notes regarding commissioning
When commissioning F_DP communication for the first time, it is recommended that the
monitoring time is initially kept at the default value in order to avoid alarms caused by the
monitoring time being exceeded.
After the F_DP communication has been successfully commissioned, the monitoring time can
then be changed to the required value, e.g. monitoring time ≥ 5 * F_DP clock cycle of the slower
component of the SPL connection with F_DP clock cycle =
$MA_SAFE_SRDP_IPO_TIME_RATIO * IPO clock cycle.
For more complex PLC user programs, it is possible that the parameterized F_ DP clock cycle
is either briefly or even permanently exceeded. This is the reason that for diagnostic purposes,
the maximum value of the F_DP clock cycle since the last time the control booted (powered-
up) is displayed in machine data $MA_INFO_SAFE_SRDP_CYCLE_TIME and in the
diagnostics screen "SI communication".
Note
It can only be ensured that the level of an output signal is correctly detected on the sender
side and transferred to the receiver if it is present for at least the monitoring time that has been
parameterized (MN_SAFE_SDP_TIMEOUT).
MD13330 $MN_SAFE_SDP_ENABLE_MASK: Enable screen form
The individual parameterizing data sets are enabled using the enable screen form. The enable
screen form is bit orientated, i.e. bit 0 activates the 1st parameterizing data set with machine
data index 0.
If a parameterizing data set is not activated, then the machine data of the corresponding SPL
connection are not evaluated.
MD13333 $MN_SAFE_SDP_CONNECTION_NR: Connection number
A parameterizing data set is assigned to an SPL connection using the connection number.
Presently, a max. of max. 16 SPL connections can be parameterized for F_SENDDP. As a
result, the value range for the connection number obtained is: 1, 2, 3 ... 16.
In the default setting, a parameterizing data set is not assigned to any SPL connection
(connection number = 0). Each active parameterizing data set must be assigned to an SPL
connection. In the case of an error, Alarm 27034 "Parameterization of MD %1[%2] invalid" is
displayed.
The connection number is, at the same time, also the index to access system variables of the
user interface of the SPL connection. The user interface involves the following system
variables:
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
8.4 Safety-related CPU-CPU communication (F_DP communication)
Connecting sensors and actuators
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