.. _gettingStartedLatchingDoc:

.. index:: single: Example; Latching a Switch

=================
Latching a Switch
=================

**Reaction: Latch** 

::

	reaction Latch {
		output:		Switch
		onExecution: 	Reset
		terminateWhen: 	Done
		internalBlock:	[
			switch Switch 	{ default: off reset: none },
			switch Done	{ default: off reset: Reset },
			trigger Reset 	{}
		]
		streams:	[
			Switch >> Select ( whenOn: off whenOff: on ) >> Switch;
			on >> Done;
		]
	}

----

**Rising Edges**


.. highlight:: rst

::

				x	x	|			x	x	x	|	
	Button	x	x	|		x	x	x	|			x	x

				x	x	x	x	x	|
	Latched	x	x	|					x	x	x	x	x


.. highlight:: stride

::
	
	switch Button {}
	switch Latched {}

	Button >> Latch () >> Latched;

----

**Different Edges**

.. highlight:: rst

::

				x	x	|			x	x	x	|	
	Button	x	x	|		x	x	x	|			x	x

				x	x	x	x	x	x	x	x	|
	Latched	x	x	|								x	x


.. highlight:: stride

::
	
	switch Button {}
	switch Latched {}

	Button >> OnEdge ( edge: [ 'Rising', 'Falling' ] ) >> Latch () >> Or () >> Latched;