Siemens S5-155U System Manual page 379

Enable input
Switching off the enable input
System Manual
C79000-B8576-C109-03
The enable circuit requires an external 24 V voltage at enable inputs
F+/F- in the front connector. If there is no voltage at F+/F-, the
modules will not acknowledge.
When the front connector is swivelled away from the front strip of the
module, the supply of power to the enable input is interrupted, i.e. the
module is switched off and can no longer be addressed by the user
program: a timeout (QVZ) occurs in the CC.
The 460 module additionally offers the facility for changing the
enable mode. The module has a jumper accessible from above in the
vicinity of the addressing switch.
When the enable jumper is inserted, you can define the behaviour of
the 460 analog input module as follows:
• • When the enable voltage and load voltage are obtained from the
same load supply, a shutdown of the 24 V load voltage will result
in a timeout.
• • When the enable voltage and load voltage are obtained from
different load supplies, a shutdown of the 24 V load voltage will
not result in a timeout. (With the 460-4UA11/12 modules, a
shutdown of the load voltage will result in a timeout.)
Enable Jumper
Figure 9-2 Enable Input and Enable Jumper
Jumper inserted: Enable input (F+/F-) active (factory setting)
Jumper open: Enable input (F+/F-) switched off
Examples of functioning of the enable inputs:
• • To switch off individual subprocesses, i.e. outputs of various
modules can be operated from a common load supply and yet
activated separately.
• • The load voltage of individual modules can be monitored without
additional circuitry. Any reactions to failure of the load voltage
can be programmed in the QVZ (timeout) organization block.
The 460 Analog Input Module
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