Fields Common to All Record Types¶
This section contains a description of the fields that are common to all record types. These fields are defined in dbCommon.dbd.
See also Fields Common to Input Record Types and Fields Common to Output Record Types.
Operator Display Parameters¶
The NAME field contains the record name which must be unique within an EPICS Channel Access name space. The name is supplied by the application developer and is the means of identifying a specific record. The name has a maximum length of 60 characters and should use only this limited set of characters:
a-z A-Z 0-9 _ - : [ ] < > ;
The DESC field may be set to provide a meaningful description of the record’s purpose. Maximum length is 40 characters.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
NAME |
Record Name |
STRING [61] |
No |
Yes |
No |
No |
|
DESC |
Descriptor |
STRING [41] |
Yes |
Yes |
Yes |
No |
Scan Fields¶
These fields contain information related to how and when a record processes. A few records have unique fields that also affect how they process. These fields, if any, will be listed and explained in the section for each record.
The SCAN field specifies the scanning period for periodic record scans or the scan type for non-periodic record scans. The default set of values for SCAN can be found in menuScan.dbd.
The choices provided by this menu are:
Passivefor the record scan to be triggered by other records or Channel AccessEventfor event-driven scanI/O Intrfor interrupt-driven scanA set of periodic scan intervals
Additional periodic scan rates may be defined for individual IOCs by making a
local copy of menuScan.dbd and adding more choices as required. Periodic scan
rates should normally be defined in order following the other scan types, with
the longest periods appearing first. Scan periods can be specified with a unit
string of second/seconds, minute/minutes, hour/hours or
Hertz/Hz. Seconds are used if no unit is included in the choice string.
For example these rates are all valid:
1 hour
0.5 hours
15 minutes
3 seconds
1 second
2 Hertz
The PINI field specifies record processing at initialization. If it is set to YES during database configuration, the record is processed once at IOC initialization (before the normal scan tasks are started).
The PHAS field orders the records within a specific SCAN group. This is not meaningful for passive records. All records of a specified phase are processed before those with higher phase number. It is generally better practice to use linked passive records to enforce the order of processing rather than a phase number.
The EVNT field specifies an event number. This event number is used if the
SCAN field is set to Event. All records with scan type Event and the
same EVNT value will be processed when a call to post_event for EVNT is made.
The call to post_event is: post_event(short event_number).
The PRIO field specifies the scheduling priority for processing records
with SCAN=I/O Event and asynchronous record completion tasks.
The DISV field specifies a “disable value”. Record processing cannot begin when the value of this field is equal to the value of the DISA field, meaning the record is disabled. Note that field values of a record can be changed by database or Channel Access puts, even if the record is disabled.
The DISA field contains the value that is compared with DISV to determine if the record is disabled. A value is obtained for the DISA field from the SDIS link field before the IOC tries to process the record. If SDIS is not set, DISA may be set by some other method to enable and disable the record.
The DISS field defines the record’s “disable severity”. If this field is not NO_ALARM and the record is disabled, the record will be put into alarm with this severity and a status of DISABLE_ALARM.
If the PROC field of a record is written to, the record is processed.
The LSET field contains the lock set to which this record belongs. All records linked in any way via input, output, or forward database links belong to the same lock set. Lock sets are determined at IOC initialization time, and are updated whenever a database link is added, removed or altered.
The LCNT field counts the number of times dbProcess finds the record active during successive scans, i.e. PACT is TRUE. If dbProcess finds the record active MAX_LOCK times (currently set to 10) it raises a SCAN_ALARM.
The PACT field is TRUE while the record is active (being processed). For asynchronous records PACT can be TRUE from the time record processing is started until the asynchronous completion occurs. As long as PACT is TRUE, dbProcess will not call the record processing routine. See Application Developers Guide for details on usage of PACT.
The FLNK field is a link pointing to another record (the “target” record).
Processing a record with the FLNK field set will trigger processing of the
target record towards the end of processing the first record (but before PACT is
cleared), provided the target record’s SCAN field is set to Passive. If the
FLNK field is a Channel Access link it must point to the PROC field of the
target record.
The SPVT field is for internal use by the scanning system.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
SCAN |
Scan Mechanism |
MENU menuScan |
Yes |
Yes |
Yes |
No |
|
PINI |
Process at iocInit |
MENU menuPini |
Yes |
Yes |
Yes |
No |
|
PHAS |
Scan Phase |
SHORT |
Yes |
Yes |
Yes |
No |
|
EVNT |
Event Name |
STRING [40] |
Yes |
Yes |
Yes |
No |
|
PRIO |
Scheduling Priority |
MENU menuPriority |
Yes |
Yes |
Yes |
No |
|
DISV |
Disable Value |
SHORT |
Yes |
1 |
Yes |
Yes |
No |
DISA |
Disable |
SHORT |
No |
Yes |
Yes |
No |
|
SDIS |
Scanning Disable |
INLINK |
Yes |
Yes |
Yes |
No |
|
PROC |
Force Processing |
UCHAR |
No |
Yes |
Yes |
Yes |
|
DISS |
Disable Alarm Sevrty |
MENU menuAlarmSevr |
Yes |
Yes |
Yes |
No |
|
LCNT |
Lock Count |
UCHAR |
No |
Yes |
No |
No |
|
PACT |
Record active |
UCHAR |
No |
Yes |
No |
No |
|
FLNK |
Forward Process Link |
FWDLINK |
Yes |
Yes |
Yes |
No |
|
SPVT |
Scan Private |
NOACCESS |
No |
No |
No |
No |
Alarm Fields¶
Alarm fields indicate the status and severity of record alarms, or determine how and when alarms are triggered. Of course, many records have alarm-related fields not common to all records. Those fields are listed and explained in the appropriate section on each record.
The STAT field contains the current alarm status.
The SEVR field contains the current alarm severity.
The AMSG string field may contain more detailed information about the alarm.
The STAT, SEVR and AMSG fields hold alarm information as seen outside of the database. The NSTA, NSEV and NAMSG fields are used during record processing by the database access, record support, and device support routines to set new alarm status and severity values and message text. Whenever any software component discovers an alarm condition, it calls one of these routines to register the alarm:
recGblSetSevr(precord, new_status, new_severity);
recGblSetSevrMsg(precord, new_status, new_severity, "Message", ...);
These check the current alarm severity and update the NSTA, NSEV and NAMSG fields if appropriate so they always relate to the highest severity alarm seen so far during record processing. The file alarm.h defines the allowed alarm status and severity values. Towards the end of record processing these fields are copied into the STAT, SEVR and AMSG fields and alarm monitors triggered.
The ACKS field contains the highest unacknowledged alarm severity.
The ACKT field specifies whether it is necessary to acknowledge transient alarms.
The UDF indicates if the record’s value is UnDeFined. Typically this is caused by a failure in device support, the fact that the record has never been processed, or that the VAL field currently contains a NaN (not a number) or Inf (Infinite) value. UDF defaults to TRUE but can be set in a database file. Record and device support routines which write to the VAL field are generally responsible for setting and clearing UDF.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
STAT |
Alarm Status |
MENU menuAlarmStat |
No |
UDF |
Yes |
No |
No |
SEVR |
Alarm Severity |
MENU menuAlarmSevr |
No |
Yes |
No |
No |
|
AMSG |
Alarm Message |
STRING [40] |
No |
Yes |
No |
No |
|
NSTA |
New Alarm Status |
MENU menuAlarmStat |
No |
Yes |
No |
No |
|
NSEV |
New Alarm Severity |
MENU menuAlarmSevr |
No |
Yes |
No |
No |
|
NAMSG |
New Alarm Message |
STRING [40] |
No |
Yes |
No |
No |
|
ACKS |
Alarm Ack Severity |
MENU menuAlarmSevr |
No |
Yes |
No |
No |
|
ACKT |
Alarm Ack Transient |
MENU menuYesNo |
Yes |
YES |
Yes |
No |
No |
UDF |
Undefined |
UCHAR |
Yes |
1 |
Yes |
Yes |
Yes |
Device Fields¶
The RSET field contains the address of the Record Support Entry Table. See the Application Developers Guide for details on usage.
The DSET field contains the address of Device Support Entry Table. The value of this field is determined at IOC initialization time. Record support routines use this field to locate their device support routines.
The DPVT field is is for private use of the device support modules.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
RSET |
Address of RSET |
NOACCESS |
No |
No |
No |
No |
|
DSET |
DSET address |
NOACCESS |
No |
No |
No |
No |
|
DPVT |
Device Private |
NOACCESS |
No |
No |
No |
No |
Debugging Fields¶
The TPRO field can be used to trace record processing. When this field is non-zero and the record is processed, a trace message will be be printed for this record and any other record in the same lock-set that is triggered by a database link from this record. The trace message includes the name of the thread doing the processing, and the name of the record being processed.
The BKPT field indicates if there is a breakpoint set at this record. This supports setting a debug breakpoint in the record processing. STEP through database processing can be supported using this.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
TPRO |
Trace Processing |
UCHAR |
No |
Yes |
Yes |
No |
|
BKPT |
Break Point |
NOACCESS |
No |
No |
No |
No |
Miscellaneous Fields¶
The ASG string field sets the name of the access security group used for this
record. If left empty, the record is placed in group DEFAULT.
The ASP field is private for use by the access security system.
The DISP field can be set to a non-zero value to reject puts from outside of the IOC (i.e. via Channel Access or PV Access) to any field of the record other than to the DISP field itself. Field changes and record processing can still be instigated from inside the IOC using DB links and the IOC scan mechanisms.
The DTYP field specifies the device type for the record. Most record types have their own set of device types which are specified in the IOC’s database definition file. If a record type does not call any device support routines, the DTYP and DSET fields are not used.
The MLOK field contains a mutex which is locked by the monitor routines in dbEvent.c whenever the monitor list for this record is accessed.
The MLIS field holds a linked list of client monitors connected to this record. Each record support module is responsible for triggering monitors for any fields that change as a result of record processing.
The PPN field contains the address of a putNotify callback.
The PPNR field contains the next record for PutNotify.
The PUTF field is set to TRUE if dbPutField caused the current record processing.
The RDES field contains the address of dbRecordType
The RPRO field specifies a reprocessing of the record when current processing completes.
The TIME field holds the time stamp when this record was last processed.
The UTAG field can be used to hold a site-specific 64-bit User Tag value that is associated with the record’s time stamp.
The TSE field value indicates the mechanism to use to get the time stamp:
0— Get the current time as normal-1— Ask the time stamp driver for its best source of the current time, if available.-2— Device support sets the time stamp and the optional User Tag from the hardware.Positive values (normally between 1-255) get the time of the last occurance of the numbered generalTime event.
The TSEL field contains an input link for obtaining the time stamp. If this link points to the TIME field of a record then the time stamp and User Tag of that record are copied directly into this record (Channel Access links can only copy the time stamp, not the User Tag). If the link points to any other field, that field’s value is read and stored in the TSE field which is then used to provide the time stamp as described above.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
|---|---|---|---|---|---|---|---|
ASG |
Access Security Group |
STRING [29] |
Yes |
Yes |
Yes |
No |
|
ASP |
Access Security Pvt |
NOACCESS |
No |
No |
No |
No |
|
DISP |
Disable putField |
UCHAR |
Yes |
Yes |
Yes |
No |
|
DTYP |
Device Type |
DEVICE |
Yes |
Yes |
Yes |
No |
|
MLOK |
Monitor lock |
NOACCESS |
No |
No |
No |
No |
|
MLIS |
Monitor List |
NOACCESS |
No |
No |
No |
No |
|
PPN |
pprocessNotify |
NOACCESS |
No |
No |
No |
No |
|
PPNR |
pprocessNotifyRecord |
NOACCESS |
No |
No |
No |
No |
|
PUTF |
dbPutField process |
UCHAR |
No |
Yes |
No |
No |
|
RDES |
Address of dbRecordType |
NOACCESS |
No |
No |
No |
No |
|
RPRO |
Reprocess |
UCHAR |
No |
Yes |
No |
No |
|
TIME |
Time |
NOACCESS |
No |
No |
No |
No |
|
UTAG |
Time Tag |
UINT64 |
No |
Yes |
No |
No |
|
TSE |
Time Stamp Event |
SHORT |
Yes |
Yes |
Yes |
No |
|
TSEL |
Time Stamp Link |
INLINK |
Yes |
Yes |
Yes |
No |