Instructions:
The latch function cannot generate a process alarm with the "FM350-1". However, it is possible to parameterize a process alarm for the "zero crossing".
The load value on the "FM350-1" must always be zero. Then with the latch process (positive edge at the DI start) the current counter value is set to the load value "zero" and the current counter value is saved.
Setting the counter value to the load value "zero" generates the "zero crossing" process alarm. Thus it is possible to read out the current latch value in the process alarm OB (e.g. OB40).
The latch value can be read directly via the I/O interface of the "FM350-1". The first 4 bytes at this interface contain the latch value.

Example:
The start address of the "FM350-1" from the Hardware Configuration is 256. With the "L PED 256" command you can read the current latch value.

The following conditions must be met:

• The load value must always be "zero".
• You must make the following settings when assigning the parameters of the "FM 350-1":
  Select "Latch/Retrigger" as latch function.

( 8 KB )
Fig. 01

The alarm selection must also be set to "Process":

( 5 KB )
Fig. 02

Parameterize the process alarm release to "zero crossing":

( 7 KB )
Fig. 03

Keywords:
Alarm configuration