BECKHOFF EL6900-FB - Manual (Page 19)

Function blocks
Function blocks for TwinSAFE logic terminals 17
3 Function blocks
The function blocks have a specified functionality that still must be configured via a parameter. The inputs
or outputs of a function block can be inputs or outputs of a local process image, but function block outputs
and inputs can be can be linked.
3.1 The AND function block
3.1.1 Functional description
With the FB AND several input signals can be linked via AND to one output signal. In addition each input
can still be set even if the input signal is a normally closed contact (Break contact) or normally open
contact (Make contact). A normally open contact means that the corresponding input signal is negated,
before it affects the AND.
The AndIn1 input differs from the AndIn2-AndIn8 inputs in such a way that it can also be linked with a
standard input. This makes it possible to switch off a safe output using a standard signal. Outputs cannot
be switched on but only released using a standard signal, since at least two inputs must always be linked
for FB AND (and the second input is a safe one, which prevents switching on).
Figure 3-1: AND function block