This section describes fields that are found in many output record types. These fields usually have the same meaning whenever they are used.
See also Fields Common to All Record Types and Fields Common to Input Records.
The OUT field specifies an output link. It is used by the device support routines to decide where to send output. For soft records, it can be a constant, a database link, or a channel access link. If the link is a constant, the result is no output.
The DTYP field specifies the name of the device support module that will input values. Each record type has its own set of device support routines. If a record type does not have any associated device support, DTYP is meaningless.
The VAL field contains the desired value before any conversions to raw output have been performed.
The OVAL field is used to decide when to invoke monitors. Archive and value change monitors are invoked if OVAL is not equal to VAL. If a record type needs to make adjustments, OVAL is used to enforce the maximum rate of change limit before converting the desired value to a raw value.
The RVAL field contains - whenever possible - the actual value sent to the hardware itself or to the associated device driver.
The RBV field contains - whenever possible - the actual read back value obtained from the hardware itself or from the associated device driver.
Normally two soft output device support modules are provided, Soft Channel and and Raw Soft Channel. Both write a value through the output link OUT. The Soft Channel module writes output from the value associated with OVAL or VAL (if OVAL does not exist). The Raw Soft Channel support module writes the value associated with the RVAL field after conversion has been performed.
The device support write routine normally calls
dbPutLink() which writes a value through the OUT link,
and returns the status from that call.
The DOL field is a link from which the desired output value can be fetched. DOL can be a constant, a database link, or a channel access link. If DOL is a database or channel access link and OMSL is closed_loop, then VAL is obtained from DOL.
The OMSL field selects the output mode.
This field has either the value
DOL is used to fetch VAL only if OMSL has the value
By setting this field a record can be switched between supervisory and closed loop mode of operation.
While in closed loop mode,
the VAL field cannot be set via dbPuts.
The fields DOL and OMSL are used to allow the output record to be part of a closed loop control algorithm.
OMSL is meaningful only if DOL refers to a database or channel access link.
It can have the values
If the mode is
then nothing is done to VAL.
If the mode is
closed_loop and the record type does not contain an OIF field,
then each time the record is processed,
VAL is set equal to the value obtained from the location referenced by DOL.
If the mode is
closed_loop in record types with an OIF field and OIF is Full,
VAL is set equal to the value obtained from the location referenced by DOL; if OIF is Incremental VAL is incremented by the value obtained from DOL.
The IVOA field specifies the output action for the case that the record is put into an INVALID alarm severity. IVOA can be one of the following actions:
Don't drive outputs
Set output to IVOV
The IVOV field contains the value for the IVOA action
Set output to IVOV in engineering units.
If a new severity has been set to INVALID and IVOA is
Set output to IVOV,
then VAL is set to IVOV and converted to RVAL before device support is called.
Whenever an output record is put into INVALID alarm severity, IVOA specifies an action to take. The record support process routine for each output record contains code which performs the following steps.
Continue normallythen call
Don't drive outputsthen do not write output.
Set output to IVOVthen set VAL to IVOV, call
convert()if necessary, and then call
The SIMM field controls simulation mode. It has either the value YES or NO. By setting this field to YES, the record can be switched into simulation mode of operation. While in simulation mode, output will be forwarded through SIOL instead of OUT.
The SIML field specifies the simulation mode location. This field can be a constant, a database link, or a channel access link. If SIML is a database or channel access link, then SIMM is read from SIML. If SIML is a constant link then SIMM is initialized with the constant value, but can be changed via database or channel access puts.
The SIOL field is a link that the output value is written to when the record is in simulation mode.
The SIMS field specifies the simulation mode alarm severity. When this field is set to a value other than NO_ALARM and the record is in simulation mode, it will be put into alarm with this severity and a status of SIMM_ALARM.
The SDLY field specifies a delay (in seconds) to implement asynchronous processing in simulation mode. A positive SDLY value will be used as delay between the first and second phase of processing in simulation mode. A negative value (default) specifies synchronous processing.
The SSCN field specifies the SCAN mechanism to be used in simulation mode. This is specifically useful for 'I/O Intr' scanned records, which would otherwise never be scanned in simulation mode.
An output record can be switched into simulation mode of operation by setting the value of SIMM to YES. During simulation, the record will be put into alarm with a severity of SIMS and a status of SIMM_ALARM. While in simulation mode, output values, in engineering units, will be written to SIOL instead of OUT. However, the output values are never converted. Also, while the record is in simulation mode, there will be no calls to device support during record processing.
Normally output records contain a private
writeValue() routine which performs the following steps:
dbGetLink()to get a new value for SIMM if SIML is a DB_LINK or a CA_LINK.
dbPutLink()to write the output value from VAL or OVAL to SIOL.
Otherwise (record is in first phase of an asynchronous processing), set up a callback processing with the delay specified in SDLY.