Forced Checking Procedure Of Spl Signals - Siemens SINUMERIK 840D sl Function Manual

Connecting Sensors/Actuators
7.1 Safety–related input/output signals
Note
System–related minimum tolerance time
2 x PLC cycle time (maximum cycle) + 1 x IPO cycle time
7.1.2

Forced checking procedure of SPL signals

Basic principles
Safety–related input/output signals including the connecting cables to the I/O
(peripherals) and the sensors and actuators connected to them must always be
subject to a forced–checking procedure (see Chapter 5.3 "Forced checking proce-
dure").
The scope of the forced checking procedure should be implemented corresponding
to the subsequent conditions.
This means that the selection of a suitable forced checking procedure concept de-
pends on the specific application and the specific sensor and/or actuator; this deci-
sion must be made by the user. In this scope, the user must configure the forced
checking procedure.
SPL signals
The forced checking procedure of SPL signals is a part of the SPL functionality
(see Chapter 7.3 "Safe programmable logic (SPL))".
Once the external safety circuit has been wired, a two–channel SPL has been
created and the relevant safety functions configured and checked with an accep-
tance test, the long–term reliability of this function, verified using an acceptance
test, can be ensured:
S External inputs/outputs
The external inputs/outputs of the SPL ($A_INSE or $A_OUTSE) must be sub-
ject to a forced checking procedure to ensure that faults do not accumulate over
a period of time which would mean that both monitoring channels could fail.
S Internal inputs/outputs
Internal inputs/outputs ($A_INSI, $A_OUTSI), markers ($A_MARKERSI) etc.
($A_TIMERSI) do not have to be subject to a forced checking procedure. It will
always be possible to detect an error at these locations due to the differing two–
channel responses of the external inputs/outputs or the NCK/drive monitoring
channels; crosswise data comparison is carried out at both ends of the re-
sponse chain to detect any errors.
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 05.2008 Edition
© Siemens AG 2008 All Rights Reserved
05.08