User:Carsten Milkau/RS-Latch - Revision history

Carsten Milkau: Carsten Milkau moved page Carsten Milkau/RS-Latch to User:Carsten Milkau/RS-Latch: This was supposed to be a user page.

2018-07-18T22:08:42Z

Carsten Milkau moved page Carsten Milkau/RS-Latch to User:Carsten Milkau/RS-Latch: This was supposed to be a user page.

Carsten Milkau: /* RS-latch */

2018-07-18T21:42:08Z

‎RS-latch

Carsten Milkau: /* Illegal State */

2018-07-18T21:38:09Z

‎Illegal State

Carsten Milkau: /* Connectors */

2018-07-18T21:30:00Z

‎Connectors

Carsten Milkau: /* RS-latch */ illegal state

2018-07-18T21:25:19Z

‎RS-latch: illegal state

Carsten Milkau: /* Using Logic Select Units */

2018-07-18T21:17:40Z

‎Using Logic Select Units

Carsten Milkau: /* Using Logic Select Units */

2018-07-18T21:16:08Z

‎Using Logic Select Units

Carsten Milkau: /* RS-latch */ image

2018-07-18T20:58:44Z

‎RS-latch: image

Carsten Milkau: Introduction

2018-07-18T20:45:03Z

Introduction

New page

== RS-latch ==

An RS-latch is a circuit that stores which of its inputs was last "on". It has typically two inputs: input ''reset'' storing value "0" and input ''set'' storing value "1", hence the name. It can have multiple outputs, which typically differ mostly in their behavior when multiple inputs are "on" at the same time.

{| class="wikitable"
|+ value table
|-
!colspan="4"|'''inputs'''||colspan="4"|'''outputs'''
|-
!reset||set||output1 (previous)||output2 (previous)||output1||output2
|-
|0||0||''x''||''y''||''y''||''x''
|-
|0||1||''x''||''y''||0||0
|-
|1||0||''x''||''y''||1||1
|-
|1||1||''x''||''y''||0||1
|}

It is possible to define a variant with more than two values. The values stored need not necessarily be 0 and 1.

=== Connectors ===

* Enabled: if 1, store ''data'', else do nothing.
* Data: input
* Output: stored value

=== Using Logic Select Unit and Logic Reader ===

[[File:D-latch.png|thumb|D-latch using select unit and reader]]

This d-latch can store any value. It works in two steps:

<ol>
<li>a Logic Select Unit determines whether to store the last output or the "data" input using the "enabled" input. i.e.
<pre> if enabled
then store = data
else store = output</pre></li>
<li>a [[Kit_(Logic_I/O)#Logic_Reader|Logic Reader]] mirrors the value to be stored and feeds it back into the select unit so it can circulate (effectively being stored). This would be obsolete if the select unit could read its own output.
<pre> output = store</pre></li>
</ol>

{| class="wikitable"
|+ Circuit setup
|-
! Unit name || Unit type || Connector / Setting || Source / Value
|-
| select 1 || Logic Select Unit || select || '''enabled''' (input)
|-
| || || 0 (input 1) || reader 1
|-
| || || 1 (input 2) || '''data''' (input)
|-
| reader 1 || Logic Reader || in || select 1
|-
| || || var || setting
|-
| || || out || '''output''' (output)
|}

@@ Line 1: / Line 1: @@
-== RS-latch ==
+An RS-latch is a circuit that stores which of its inputs was last "on". It has typically two inputs: input ''reset'' storing value "0" and input ''set'' storing value "1", hence the name. It can have multiple outputs (possibly inverted), which typically differ mostly in their behavior when multiple inputs are "on" at the same time. Usually, it is considered illegal to set more than one input to "on", but sometimes this is used deliberately (e.g. when constructing an [[Edge-Triggered RS-Latch]]).
-An RS-latch is a circuit that stores which of its inputs was last "on". It has typically two inputs: input ''reset'' storing value "0" and input ''set'' storing value "1", hence the name. It can have multiple outputs (possibly inverted), which typically differ mostly in their behavior when multiple inputs are "on" at the same time. Usually, it is considered illegal to set more than one input to "on", but sometimes this is used deliberately (e.g. when constructing an [[Edge-Triggered RS-Latch]]).
+== Definition ==
 {| class="wikitable"
@@ Line 32: / Line 32: @@
 If multiple inputs are on at the same time, the latch is considered in "illegal state". In principle, the RS-latch assumes both values at once, which circulate through the latch when both inputs turn off immediately (see value table), i.e. the latch becomes a [[Clock]]. This is usually undesired, but can be useful in some cases.
-=== Using Logic Select Units ===
+== Implementation Using Logic Select Units ==
 [[File:RS-Latch Using Select Units.png|thumb|An RS-Latch implemented using two Logic Select Units and two Logic Memory units]]

@@ Line 27: / Line 27: @@
 * Output1: Stored value (first value if in illegal state)
 * Output2: Stored value (second value if in illegal state)
 === Using Logic Select Units ===

@@ Line 23: / Line 23: @@
 === Connectors ===
-* Enabled: if 1, store ''data'', else do nothing.
+* Reset: Stores the first value (typically 0)
-* Data: input
+* Set: Stores the second value (typically 1)
-* Output: stored value
+* Output1: Stored value (first value if in illegal state)
 === Using Logic Select Units ===

@@ Line 42: / Line 42: @@
 |           ||              || 0 (input 1)         || select 2
 |-
-|           ||              || 1 (input 2)         || memory 1 (constant)
+|           ||              || 1 (input 2)         || "0" (constant)
 |-
 |           ||              || output              || '''output1''' (output)
@@ Line 50: / Line 50: @@
 |           ||              || 0 (input 1)         || select 1
 |-
-|           ||              || 1 (input 2)         || memory 2 (constant)
+|           ||              || 1 (input 2)         || "1" (constant)
 |-
 |           ||              || output              || '''output2''' (output)
 |}

← Older revision	Revision as of 22:08, 18 July 2018
(No difference)

@@ Line 27: / Line 27: @@
 * Output: stored value
-=== Using Logic Select Unit and Logic Reader ===
+=== Using Logic Select Units ===
 [[File:RS-Latch Using Select Units.png|thumb|An RS-Latch implemented using two Logic Select Units and two Logic Memory units]]
-This d-latch can store any value. It works in two steps:
+This RS-latch can store arbitrary values. It can also easily be extended to support more than two different values. It consists of a loop of [[Kit (Logic Processor)#Logic Select Unit|Logic Select Units]], each connected to a dedicated memory cell (or other data source). If all inputs are off, the values circulate in the loop. If one input is on, its corresponding value is read from the respective memory cell and replaces all values in the loop (unless an additional input is on).
 {| class="wikitable"
@@ Line 48: / Line 38: @@
 ! Unit name || Unit type    || Connector / Setting || Source / Value
 |-
-| select 1  || Logic Select Unit  || select         || '''enabled''' (input)
+| select 1  || Logic Select Unit  || select        || '''reset''' (input)
 |-
-|           ||              || 0 (input 1)    || reader 1
+|           ||              || 1 (input 2)         || memory 1 (constant)
 |-
-|           ||              || 1 (input 2)    || '''data''' (input)
+|           ||              || output              || '''output1''' (output)
 |-
-| reader  1 || Logic Reader || in             || select 1
+|           ||              || 0 (input 1)         || select 1
 |-
-|           ||              || var            || setting
+|           ||              || 1 (input 2)         || memory 2 (constant)
 |-
-|           ||              || out            || '''output''' (output)
+|           ||              || output              || '''output2''' (output)
 |}