Instruction manual

Digital Latches
890USE18300 September 2003 159
Physical Output The output from a low-level digital D-latch block is a Boolean 1 or 0. The output is
latched when the trigger value is 0 and unlatched when the trigger value is 1.
If the output is not inverted, it echoes the current operational input when the latch
trigger is high, and it latches the value of the operational input at the moment that
the trigger drops from 1 to 0.
If the output is inverted, it echoes the inverse of the current operational input when
the latch trigger is high, and it latches a value that is the inverse of the value of the
operational input at the moment that the trigger drops from 1 to 0.
The physical output (See Configuring the Physical Output from a Reflex Block,
p. 27) needs to be mapped to an action module:
The action module may be a digital output module on the island bus. In this case,
you need to specify one of the digital output channels as the destination for the
block’s output.
If the latch is the first block in a nested reflex action (See Nesting Two Reflex
Blocks, p. 36), the action module needs to be the same action module as the one
specified for the second reflex block. Specify the channel as None.
When the output from a block is mapped to a channel on a digital output module,
that channel becomes dedicated to the reflex action and can no longer use data from
the fieldbus master to update its field device. The fieldbus master still has the ability
to write data to this bit address in the NIM, and the reflex action editor lets you use
this data from the fieldbus master as an input to the block.