Passivation And Reintegration Of Input/Output Channels; Passivation - General - Siemens SIMATIC PCS 7 Operating Manual

7.7

Passivation and reintegration of input/output channels

7.7.1

Passivation - general

Passivation means that in the event of an error, one or a number of channels on an F signal
module are switched to a safe state. In the event of a channel error (a faulty sensor, for
example), only the affected channel is passivated.
In the event of a module error (a communication error, for example), all channels on the fail-
safe I/O module are passivated.
If an F signal module detects an error, it switches the affected channel or all of its channels
to the safe state; in other words, the channels on this module are passivated. The fail-safe F
signal module sends a message to the F channel driver and the PCS 7 OS to indicate that it
has detected an error.
The PASS_ON input can also be used to activate and deactivate the passivation of a
channel in the safety program, e.g. by using a specific condition in the program sequence or
restart protection.
When output channels are passivated, the outputs are de-energized (set to a zero-current or
zero-voltage state). The F channel driver of a passivated digital output channel issues a
substitute value with the quality code (QUALITY) 16#48 and the QBAD output is set to 1.
When input channels are passivated, substitute values are forwarded to the safety program,
regardless of the actual process signal.
The F channel driver of a passivated digital input channel outputs substitute value 0 with
quality code (QUALITY) 16#48 and the QBAD output is set to 1. In accordance with the
parameter assignment at the SUBS_ON input, the F channel driver of an analog input
channel will output either a substitute value with quality code (QUALITY) 16#48 or the last
valid value with quality code (QUALITY) 16#44. The QBAD output is also set to 1 and, if a
substitute value is output, the QSUBS output is set to 1.
See also
F startup and (re)start protection (Page 104)
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
7.7 Passivation and reintegration of input/output channels
Configuring the safety program
107