HIMatrix 8 Safety-related Aspects of the User Program
HI 800 023 E Rev. 1.01 Page 55 of 72
Basic information on forcing can be found in the TÜV document "Maintenance Override“.
This document is available on the TÜV homepage:
http://www.tuv-fs.com or
http://www.tuvasi.com.
8.2.7 Forcing - Versions Beyond 7
Forcing can operate at two levels::
Global forcing: Global variables are forced for all applications.
Local forcing: Values of local variables are forced for an individual user program.
i
Absolutely take the following facts into account when forcing or evaluating tests
performed with forced global variables:
The force values of global variables are only valid until the user program overwrites the
values!
However, if the user program does not overwrite the values, e.g., if an EN input is set to
FALSE, the force value is used as a process value in the ensuing calculations.
Online test fields connected to forced global variables may therefore show the forced value
even if a value created by the user program is already taken into account in the following
calculations or is effective on an output.
8.2.8 Time Limits
Different time limits can be set for global or local forcing. Once the defined time has
expired, the controller stops forcing values.
It is possible to define how the HIMatrix system should behave upon expiration of the time
limit:
With global forcing, the resource is stopped or continues to run.
With local forcing, the user program is stopped or continues to run.
It is also possible to use forcing without time limit. In this case, the forcing procedure must
be stopped manually.
The person responsible for forcing must clarify in advance what effects stopping forcing
may have on the entire system!
8.2.9 Restricting the Use of Forcing
The following measures can be configured to limit the use of forcing and thus avoid
potential faults in the safety functionality due to improper use of forcing:
Configuring different user profiles with or without forcing authorization
Prohibit global forcing for a resource
Prohibit local forcing
Forcing can also be stopped immediately using a key switch.
To do so, the Force Deactivation system variable must be linked to a digital input con-
nected to a key switch.
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