Forced Checking Procedure - Siemens SINUMERIK 840D sl Function Manual

Basics regarding the safety functions integrated in the system/drive

6.3 Forced checking procedure

The following apply for the axis-specific monitoring functions: In the case of "non-steady-state"
data, tolerance values defined using machine data are used by which amount the results of
the two channels may deviate from one another without initiating a response (e.g. tolerance
for crosswise data comparison of actual positions).
A distinction is made between:
● The drive CDC between the drive and Motor Module
● Axis CDC between the NCK and drive (refer to Chapter "Safety functions integrated in the
system/drive (Page 101)").
● Communication CDC between NCK and PLC (see Chapter "Connecting I/O via
PROFIsafe (Page 184)" and Chapter "Safety-related CPU-CPU communication (F_DP
communication) (Page 215)").
● SPL-CDC between the NCK and PLC (refer to Chapter "Safe programmable logic
(Page 256)").
Error response
If the crosswise data comparison identifies an error, then this results in a stop response (refer
to Chapter "Safe Stops A-F (Page 112)").
In addition, safety alarms are output.
Note
If SGEs are quickly switched over several times, then this can initiate a STOP F.
Displaying the crosswise data comparison clock cycle
To display the actual crosswise data comparison cycle time between the NCK and drive, the
axis-specific MD36992 $MA_SAFE_CROSSCHECK_CYCLE and general MD10092
$MN_INFO_CROSSCHECK_CYCLE_TIME are used: If the monitoring clock cycle is modified,
then the crosswise comparison clock cycle is also changed.
The length of the crosswise comparison list depends on whether certain functions have been
enabled.
The CDC cycle active on an axis is displayed in the axis-specific MD36992
$MA_SAFE_CROSSCHECK_CYCLE.
The maximum CDC cycle time active on the axes is displayed in the NCK-specific MD
$MN_INFO_CROSSCHECK_CYCLE_TIME.
6.3 Forced checking procedure
Forced checking procedure, general (extract from /6/)
"...A forced checking procedure must be carried-out for all static (steady-stage) signals and
data. Within the required time (8 h), the state must change from a logical 1 to a logical 0 - or
vice versa. If the state remains static in a fault situation, then this is detected at the latest as
a result of this forced checking procedure and the subsequent comparison.
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Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated