Siemens S5-155U System Manual page 305

With an active enable input
System Manual
C79000-B8576-C199-03
This means that:
• • The module can no longer be addressed by the user program.
• • All outputs of digital output modules are set to zero.
Modules which are switched off can be removed or inserted during
operation. If this is not necessary, operate the module with the enable
input switched off.
On digital input/output modules with DC voltage inputs or outputs,
the enable circuit requires that enable inputs F+ and F- be wired in the
front connector. Enabling is achieved by applying an external voltage
to inputs F+/F-. Modules for AC voltage have a wire jumper in the
front connector.
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
wire jumper in the front connector is removed; the module is switched
off and can no longer be addressed by the user program.
When the front connector is swivelled away, i.e. the voltage is
removed from the enable inputs, a timeout (QVZ) occurs at the CPU
(see the Programming Guide for the particular CPU).
Apart from the 6ES5 458-4UC11 digital output module, all digital
input/output modules additionally offer the facility for changing the
enable mode. The modules have a jumper accessible from above in the
vicinity of the addressing switch (see Figure 8-2).
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Figure 8-2 Location of the Enable Jumper
Jumper inserted: Enable input (F+/F-) active (factory setting)
Jumper open: Enable input (F+/F-) switched off
Technical Description
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