EPICS 101 - Revision history

Tguruswamy: Adjust link text

2023-12-23T02:52:51Z

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	== What is EPICS? ==		== What is EPICS? ==

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	EPICS is a '''distributed''' control system, which means that the IOC (software) can run on a different computer as the user interfaces.		EPICS is a '''distributed''' control system, which means that the IOC (software) can run on a different computer as the user interfaces.

	This page is dedicated to the definition of basic EPICS components ([~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_101#What_is_an_IOC.3F IOC], [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_101#What_is_a_PV.3F PV], [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_101#What_is_a_record.3F record], [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_101#~~What_is_a_databases~~.3F database]). To build your own EPICS support, you can skip directly to [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~IOC_101 How does one create an IOC].		This page is dedicated to the definition of basic EPICS components ([[EPICS_101#What_is_an_IOC.3F\|IOC]], [[EPICS_101#What_is_a_PV.3F\|PV]], [[EPICS_101#What_is_a_record.3F\|record]], [[EPICS_101#What_is_a_database.3F\|database]]). To build your own EPICS support, you can skip directly to [[IOC_101\|How does one create an IOC]].

	== What is an IOC? ==		== What is an IOC? ==
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	Most of the interactive parts of user displays have PVs associated with them.		Most of the interactive parts of user displays have PVs associated with them.



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	Records are the building blocks of EPICS:		Records are the building blocks of EPICS:
	* There is a lot of different types of record, and each type is designed to perform a specific function		* There is a lot of different types of record, and each type is designed to perform a specific function
	* Records are customizable via fields that allow users to configure how they behave and monitor their state (see [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_Cheat_Sheet#Noteworthy_fields Noteworthy Fields] & [[#How to find more info about record fields]] to know how to learn about record fields)		* Records are customizable via fields that allow users to configure how they behave and monitor their state (see [[EPICS_Cheat_Sheet#Noteworthy_fields\|Noteworthy Fields]] & [[#How to find more info about record fields]] to know how to learn about record fields)
	* Records do nothing until they are processed (see [[#SCAN, PROC & FLNK fields]])		* Records do nothing until they are processed (see [[#SCAN, PROC & FLNK fields]])
	* Records vary significantly in complexity (see [[#More about records]])		* Records vary significantly in complexity (see [[#More about records]])
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	=== What is a record field? ===		=== What is a record field? ===

	Record fields are controllable or informative properties of a record. For a list of noteworthy fields, see the [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_Cheat_Sheet#Noteworthy_fields EPICS cheat sheet].		Record fields are controllable or informative properties of a record. For a list of noteworthy fields, see the [[EPICS_Cheat_Sheet#Noteworthy_fields\|EPICS cheat sheet]].

	==== SCAN, PROC & FLNK fields ====		==== SCAN, PROC & FLNK fields ====
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	** synApps record reference documentation		** synApps record reference documentation
	*** In each module's documentation directory		*** In each module's documentation directory
	**** [https://github.com/epics-modules ~~https://github.com/epics-modules]~~		**** https://github.com/epics-modules
	**** <code>/APSshare/epics/synApps_X_Y/support</code>		**** <code>/APSshare/epics/synApps_X_Y/support</code>

	== What is a ~~databases~~? ==		== What is a database? ==

	A database is just a text file with a '''.db''' (or '''.template''') extension containing a collection of records that are related.		A database is just a text file with a '''.db''' (or '''.template''') extension containing a collection of records that are related.
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	== What's next? ==		== What's next? ==

	To learn how to create your own IOC, go to [~~https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101~~ IOC 101].		To learn how to create your own IOC, go to [[IOC 101]].

Rodolakis: /* What is EPICS? */

2023-03-20T14:32:42Z

What is EPICS?

← Older revision		Revision as of 14:32, 20 March 2023
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	EPICS is a '''distributed''' control system, which means that the IOC (software) can run on a different computer as the user interfaces.		EPICS is a '''distributed''' control system, which means that the IOC (software) can run on a different computer as the user interfaces.

	This page is dedicated to the definition of basic EPICS components ([https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_for_Dummies~~#What_is_an_IOC.3F IOC], [https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_for_Dummies~~#What_is_a_PV.3F PV], [https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_for_Dummies~~#What_is_a_record.3F record], [https://wiki-ext.aps.anl.gov/blc/index.php?title=~~EPICS_for_Dummies~~#What_is_a_databases.3F database]). To build your own EPICS support, you can skip directly to [https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101 How does one create an IOC].		This page is dedicated to the definition of basic EPICS components ([https://wiki-ext.aps.anl.gov/blc/index.php?title=EPICS_101#What_is_an_IOC.3F IOC], [https://wiki-ext.aps.anl.gov/blc/index.php?title=EPICS_101#What_is_a_PV.3F PV], [https://wiki-ext.aps.anl.gov/blc/index.php?title=EPICS_101#What_is_a_record.3F record], [https://wiki-ext.aps.anl.gov/blc/index.php?title=EPICS_101#What_is_a_databases.3F database]). To build your own EPICS support, you can skip directly to [https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101 How does one create an IOC].



	== What is an IOC? ==		== What is an IOC? ==

Rodolakis at 19:32, 17 March 2023

2023-03-17T19:32:55Z

← Older revision		Revision as of 19:32, 17 March 2023
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	== What next? ==		== What's next? ==

	To learn how to create your own IOC, go to [https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101 IOC 101].		To learn how to create your own IOC, go to [https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101 IOC 101].



	== External links ==		== External links ==

Rodolakis: /* What is a databases? */

2023-03-17T19:32:36Z

What is a databases?

← Older revision		Revision as of 19:32, 17 March 2023
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			== What next? ==

			To learn how to create your own IOC, go to [https://wiki-ext.aps.anl.gov/blc/index.php?title=IOC_101 IOC 101].

	== External links ==		== External links ==

Rodolakis: /* How to find more info about record fields */

2023-03-17T19:28:46Z

How to find more info about record fields

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	To find documentation for a specific field you need to know/find answers to the following questions:		To find documentation for a specific field you need to know/find answers to the following questions:
	* Is the field common to all or input/output record types?		* Is the field common to all record or only input/output record types?
	* If not, does the record come from EPICS base or a different EPICS module (synApps)?		* If not, does the record come from EPICS base or a different EPICS module (synApps)?
	** The [https://epics.anl.gov/base/R7-0/7-docs/RecordReference.html EPICS base record reference documentation] is the best place to find information about record types that come from EPICS base. <br>Field documentation appears in multiple locations:		** The [https://epics.anl.gov/base/R7-0/7-docs/RecordReference.html EPICS base record reference documentation] is the best place to find information about record types that come from EPICS base. <br>Field documentation appears in multiple locations:

Rodolakis: /* What is an IOC? */

2023-03-17T19:16:42Z

What is an IOC?

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	Any client, locally or on the network, can read and/or write a process variable using either '''channel access''' (CA) or '''PVaccess''' (PVA) network protocols. Clients might be another IOC, a GUI display manager (medm/caqtdm/CSS), or any other program with support for the EPICS protocols. Only the name of the process variable (in the form <code>'''prefix:record_name.field_name'''</code>) is required to read or write a PV.		Any client, locally or on the network, can read and/or write a process variable using either '''channel access''' (CA) or '''PVaccess''' (PVA) network protocols. Clients might be another IOC, a GUI display manager (medm/caqtdm/CSS), or any other program with support for the EPICS protocols. Only the name of the process variable (in the form <code>'''prefix:record_name.field_name'''</code>) is required to read or write a PV.

	Note ~~that~~:		<u>Note</u>:
	* IOCs used to run on VMEs, but nowadays it runs on anything.		* IOCs used to run on VMEs, but nowadays it runs on anything.
	* IOCs usually talks to hardware, but that isn’t a requirement.		* IOCs usually talks to hardware, but that isn’t a requirement.
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	'''Records''' and '''databases''' (lists of records) are configuration files describing the initial setup for '''PVs'''; the '''IOC''' is the software that manages the behavior of PVs and communication to get/set their values.		'''Records''' and '''databases''' (lists of records) are configuration files describing the initial setup for '''PVs'''; the '''IOC''' is the software that manages the behavior of PVs and communication to get/set their values.



	== What is a PV? ==		== What is a PV? ==

Rodolakis: /* Forward Links */

2023-03-17T19:16:14Z

Forward Links

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	Forward links look like output links; they are purple on user displays, but they don't auto-populate with process & alarm commands.		Forward links look like output links; they are purple on user displays, but they don't auto-populate with process & alarm commands.
	Forward links cause the linked record to process when the record containing the forward link is processed		Forward links cause the linked record to process when the record containing the forward link is processed:
	* Linked record is in the same IOC ('''PROC''' field for linked record is optional):		* Linked record is in the same IOC ('''PROC''' field for linked record is optional):
	** <code>record_name.FLNK = linked_record_name</code>		** <code>record_name.FLNK = linked_record_name</code>

Rodolakis: /* Forward Links */

2023-03-17T19:15:37Z

Forward Links

← Older revision		Revision as of 19:15, 17 March 2023
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	==== Forward Links ====		==== Forward Links ====

	Forward ~~link~~ look like output links; they are purple on user displays, but they don't auto-populate with process & alarm commands.		Forward links look like output links; they are purple on user displays, but they don't auto-populate with process & alarm commands.
	Forward ~~link causes~~ the linked record to process when the record containing the forward link is processed		Forward links cause the linked record to process when the record containing the forward link is processed
	* Linked record is in the same IOC ('''PROC''' field for linked record is optional):		* Linked record is in the same IOC ('''PROC''' field for linked record is optional):
	** <code>record_name.FLNK = linked_record_name</code>		** <code>record_name.FLNK = linked_record_name</code>

Rodolakis: /* Output Links */

2023-03-17T19:14:56Z

Output Links

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	<u>Note</u>:		<u>Note</u>:
	* The default link process command, <code>NPP</code>, is '''almost never the desired behavior''' for output links. Change <code>NPP</code> to <code>PP</code> immediately and revert if problems are discovered.		* The default link process command, <code>NPP</code>, is '''almost never the desired behavior''' for output links. Change <code>NPP</code> to <code>PP</code> immediately and revert if problems are discovered.
	* If the target PV is itself a link field, you must specify the command <code>CA</code>; if you want to wait for completion in this case, you must use either the '''sseq''' or the '''sCalcout''' record, select <code>CA</code> and set the link's '''WAIT''' field to <code>Wait</code>		* If the target PV is itself a link field, you must specify the command <code>CA</code>; if you want to '''wait for completion''' in this case, you must use either the '''sseq''' or the '''sCalcout''' record, select <code>CA</code> and set the link's '''WAIT''' field to <code>Wait</code>
	* ''outlinkHelp'' is accessible from userTransform and scaler screens.		* ''outlinkHelp'' is accessible from userTransform and scaler screens.

Rodolakis: /* Output Links */

2023-03-17T18:57:27Z

Output Links

← Older revision		Revision as of 18:57, 17 March 2023
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	Here are the possible process commands for an output link:		Here are the possible process commands for an output link:
	* <code>NPP</code> - Just write a value; don't process the target record; this is a default command.		* <code>NPP</code> - Just write a value; don't process the target record; this is a default command.
	* <code>PP</code> - Write a value and then process the target record. To be used if you want EPICS to wait for completion.		* <code>PP</code> - Write a value and then process the target record. To be used if you want EPICS to wait for completion. When the target record get processed, EPICS will trace it.
	* <code>CA</code> - Write a value; let the target record decide whether or not to process (as it would if you typed the value by hand); if the processing does occur, EPICS will not trace it.		* <code>CA</code> - Write a value; let the target record decide whether or not to process (as it would if you typed the value by hand); if the processing does occur, EPICS will not trace it.