Instruction manual

Analog Latches
890USE18300 September 2003 131
Latch Trigger
Input
The latch trigger may be a Boolean 1 or 0. When the value of the trigger falls from 1
to 0, the block latches the value of the analog input and the latched value becomes
the block’s output. The latched output value remains set until the trigger falls again
from 1 to 0, producing a new latched output.
The latch trigger value may be produced by:
a constant
a digital input from a module on the island
a digital output from the virtual module (See The Virtual Module, p. 28)
if the latch is the second block in a nested reflex action (See Nesting Two Reflex
Blocks, p. 36), the latch trigger input may be the output from the first reflex block
Note: At start-up, make sure that the trigger input provides a 1 to the latch block.
If the trigger is 0 when the latch becomes enabled, the latch assumes that a falling-
edge transition has just taken place and immediately latches the value. If the trigger
input is 1 when the block is enabled, the latch waits for the next falling-edge
transition before it latches a value.