EPICS Database Operations

A previously defined 'BUILDING BLOCK' with a unique structure of fields and a unique processing routine to accomplish a specific function.
'RECORD SUPPORT' refers to the processing routine and the definition of the structure of the record type.

SCANNED (PROCESSED)

Executing the record processing routine (unique to a record type) for a particular record

Basic Concepts

The IOC's fundamental responsibility is to input (MONITOR) data from the "PROCESS" (and/or the OPERATOR), manipulate it in an appropriate manner, and (optionally) output data to control the "PROCESS"
Inputs, data manipulation, and outputs are defined by the "APPLICATION DEVELOPER" by configuring "RECORDS" that become part of the IOC's "DATABASE"
The IOC's primary task is to "SCAN" the database, deciding when to and knowing how to execute predefined records

IOC Internals

Database Record Types by Category

INPUTS	ALGORITHMS	OUTPUTS
Analog Input	Calculation	Analog Output
Binary Input	PID	Binary Output
Muli-bit Binary Input	Signal Select	Multi-bit Binary Output
Digitized Analog Input	Data Compression	Stepper Motor
State	Subroutine	Timing Signal
String Input	Fanout	Permissive
Long Input	Histogram	String Output
Pulse Counter		Long Output
		Pulse Train
		Pulse Delay

Analog Input Record

struct aiRecord  {


  /* start of record common fields*/
  char  name[28];  /* Record Name */
  char  desc[28];  /* Descriptor */
  unsigned short  scan;  /* Scan Mechanism */
  unsigned short  pini;  /* Process at iocInit */
  short  phas;  /* Scan Phase */
  short  evnt;  /* Event Number */
  struct link  sdis;  /* Scanning Disable */
  unsigned short  dtyp;  /* Device Type */
  short  disv;  /* Disable Value */
  short  disa;  /* Disable */
  unsigned char  disp;  /* Disable putField */
  unsigned char  proc;  /* Force Processing */
  FAST_LOCK  mlok;  /* Monitor fastlock */
  LIST  mlis;  /* Monitor List */
  unsigned short  stat;  /* Alarm Status */
  unsigned short  sevr;  /* Alarm Severity */
  unsigned short  nsta;  /* New Alarm Status */
  unsigned short  nsev;  /* New Alarm Severity */
  char  p001[4];  /* Created Pad  */
  TS_STAMP  time;  /* Time */
  short  lset;  /* Lock Set */
  unsigned char  lcnt;  /* Lock Count */
  unsigned char  pact;  /* Record active */
  caddr_t  spvt;  /* Scan Private */
  caddr_t  rset;  /* Address of RSET */
  struct dset  *dset;  /* DSET address */
  caddr_t  dpvt;  /* Device Private */
  unsigned char  tpro;  /* Trace Processing */
  unsigned char  udf;  /* Undefined */
  unsigned short  prio;  /* Scheduling Priority */
  struct link  flnk;  /* Forward Process Link */

  /* start of ai specific fields */ 
  double  val;  /* Current EGU Value */
  struct link  inp;  /* Input Specification */
  short  prec;  /* Display Precision */
  unsigned short  linr;  /* Linearization */
  float  eguf;  /* Engineer Units Full */
  float  egul;  /* Engineer Units Low */
  char  egu[16];  /* Engineering Units */
  float  hopr;  /* High Operating Range */
  float  lopr;  /* Low Operating Range */
  float  aoff;  /* Adjustment Offset */
  float  aslo;  /* Adjustment Slope */
  float  smoo;  /* Smoothing */
  float  hihi;  /* Hihi Alarm Limit */
  float  lolo;  /* Lolo Alarm Limit */
  float  high;  /* High Alarm Limit */
  float  low;  /* Low Alarm Limit */
  unsigned short  hhsv;  /* Hihi Severity */
  unsigned short  llsv;  /* Lolo Severity */
  unsigned short  hsv;  /* High Severity */
  unsigned short  lsv;  /* Low Severity */
  double  hyst;  /* Alarm Deadband */
  double  adel;  /* Archive Deadband */
  double  mdel;  /* Monitor Deadband */
  double  lalm;  /* Last Value Alarmed */
  double  alst;  /* Last Value Archived */
  double  mlst;  /* Last Val Monitored */
  double  eslo;  /* Rawto EGU Slope */
  long  roff;  /* Raw Offset */
  caddr_t  pbrk;  /* Ptrto brkTable */
  short  init;  /* Initialized? */
  short  lbrk;  /* LastBreak Point */
  long  rval;  /* Current Raw Value */
  long  oraw;  /* Previous Raw Value */
};

Record Scanning

SCANNING MECHANISMS :

PERIODIC (.1, .2, .5, 1, 2, 5, 10 second scan)
I/O EVENT (typically a hardware interrupt)
EVENT (a 'soft' interrupt originating from elsewhere)
PASSIVE (only scans when specifically requested)
INPUT LINK with CP attribute (R3.13) (scans when a "monitor" is received from the input PV)
INPUT LINK with CPP attribute (R3.13) (scans when a "monitor" is received and the record is 'Passive'

SCAN DISABLE

Every record has a 'SCAN DISABLE FIELD' that can override the scan mechanism to inhibit the processing of the record

EPICS Database Operations

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