Fields Common to Output Record Types

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.

Output and Value Fields

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.

Device Support for Soft Records

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.

Input and Mode Select Fields

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 supervisory or closed_loop. DOL is used to fetch VAL only if OMSL has the value closed_loop. 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.

Output Mode Selection

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 supervisory or closed_loop. If the mode is supervisory, 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.

Invalid Output Action Fields

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:

• Continue normally
• 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.

Invalid Alarm Output Action

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.

• If new severity is less than INVALID, then call writeValue():
• Else do the following:
  • If IVOA is Continue normally then call writeValue().
  • If IVOA is Don't drive outputs then do not write output.
  • If IVOA is Set output to IVOV then set VAL to IVOV, call convert() if necessary, and then call writeValue().
  • If IVOA not one of the above, an error message is generated.

Simulation Fields

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.

Ths SIML 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 dbPuts.

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.

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:

• If PACT is TRUE, the device support write routine is called, status is set to its return code, and readValue returns.
• Call dbGetLink() to get a new value for SIMM if SIML is a DB_LINK or a CA_LINK.
• Check value of SIMM.
• If SIMM is NO, then call the device support write routine, set status to its return code, and return.
• If SIMM is YES, then call dbPutLink() to write the output value from VAL or OVAL to SIOL. Set alarm status to SIMM and severity to SIMS, if SIMS is greater than zero. Set status to the return code from dbPutLink() and return.
• If SIMM not one of the above, a SOFT alarm with a severity of INVALID is raised, and return status is set to -1.