RRM 3-14 Waveform
Waveform
The waveform record type is used to interface waveform digitizers. The record stores its data in arrays. The array can contain any of the supported data types.
Parameter Fields
The waveform's fields fall into the following categories:
- scan parameters
- read parameters
- operator display parameters
- run-time parameters
Scan Parameters
The waveform record has the standard fields for specifying under what circumstances the record will be processed. These fields are listed in Scan Fields. In addition, Scanning Specification explains how these fields are used. Note that I/O event scanning is only supported for those card types that interrupt.
Read Parameters
These fields are configurable by the user to specify how and from where the record reads its data. How the INP field is configured determines where the waveform gets its input. It can be a hardware address, a channel access or database link, or a constant. Only in records that use soft device support can the INP field be a channel access link, a database link, or a constant. Otherwise, the INP field must be a hardware address. See Address Specification for information on the format of hardware addresses and database links.
The DTYP field must contain the name of the appropriate device support module. The user can see a list of the device support modules currently supported at the user's local site by using the dbst utility (R3.13).
The values retrieved from the input link are placed in an array referenced by VAL. (If the INP link is a constant, elements can be placed in the array via dbPuts.) NELM specifies the number of elements that the array will hold, while FTVL specifies the data type of the elements.
The RARM field causes the device to re-arm when this field is set to 1.
| Field | Summary | Type | DCT | Initial | Access | Modify | Rec Proc Monitor | PP |
|---|---|---|---|---|---|---|---|---|
| INP | Input Link | INLINK | Yes | 0 | No | No | N/A | No |
| NELM | Number of Elements in array | ULONG | Yes | 1 | Yes | No | No | No |
| FTVL | Field Type of Value | GBLCHOICE | Yes | 0 | Yes | No | No | No |
| RARM | Rearm | SHORT | Yes | 0 | Yes | Yes | No | Yes |
Operator Display Parameters
These parameters are used to present meaningful data to the operator. They display the value and other parameters of the waveform either textually or graphically.
EGU is a string of up to 16 characters describing the units that the waveform measures. It is retrieved by the get_units record support routine.
The HOPR and LOPR fields set the upper and lower display limits for array elements referenced by the VAL field. Both the get_graphic_double and get_control_double record support routines retrieve these fields.
The PREC field determines the floating point precision with which to display the array values. It is used whenever the get_precision record support routine is called.
See Fields Common to All Record Types for more on the record name (NAME) and description (DESC) fields.
| Field | Summary | Type | DCT | Initial | Access | Modify | Rec Proc Monitor | PP |
|---|---|---|---|---|---|---|---|---|
| EGU | Engineering Units | STRING [16] | Yes | null | Yes | Yes | No | No |
| HOPR | High Operating Range | FLOAT | Yes | 0 | Yes | Yes | No | No |
| LOPR | Low Operating Range | FLOAT | Yes | 0 | Yes | Yes | No | No |
| PREC | Display Precision | SHORT | Yes | 0 | Yes | Yes | No | No |
| NAME | Record Name | STRING [29] | Yes | 0 | Yes | No | No | No |
| DESC | Description | STRING [29] | Yes | Null | Yes | Yes | No | No |
Alarm Parameters
The waveform record has the alarm parameters common to all record types. Alarm Fields lists other fields related to a alarms that are common to all record types.
Run-time Parameters
These parameters are used by the run-time code for processing the waveform. They are not configured using a configuration tool. Only the VAL field is modifiable at run-time.
VAL references the array where the waveform stores its data. The BPTR field holds the address of the array.
The NORD field holds a counter of the number of elements that have been read into the array. It is reset to 0 when the device is rearmed. The BUSY field indicates if the device is armed but has not yet been digitized.
| Field | Summary | Type | DCT | Initial | Access | Modify | Rec Proc Monitor | PP |
|---|---|---|---|---|---|---|---|---|
| VAL | Value Field | See FTVL | No | 0 | Yes | Yes | Yes | Yes |
| BPTR | Buffer Pointer | NOACCESS | No | 0 | No | No | No | No |
| NORD | Number of Elements Read | ULONG | No | 0 | Yes | No | No | No |
| BUSY | Busy | SHORT | No | 0 | Yes | No | No | No |
The following fields are used to operate the waveform in the simulation mode. See Simulation Mode for more information on the simulation mode fields.
| Field | Summary | Type | DCT | Initial | Access | Modify | Rec Proc Monitor | PP |
|---|---|---|---|---|---|---|---|---|
| SIOL | Simulation Value Location | INLINK | Yes | 0 | No | No | N/A | No |
| SIML | Simulation Mode Location | INLINK | Yes | 0 | No | No | N/A | No |
| SIMM | Simulation Mode | GBLCHOICE | No | 0 | Yes | Yes | No | No |
| SIMS | Simulation Mode Alarm Severity | GBLCHOICE | Yes | 0 | Yes | Yes | No | No |
Record Support
Record Support Routines
init_record
Using NELM and FTVL space for the array is allocated. The array address is stored in the record.
This routine initializes SIMM with the value of SIML if SIML type is CONSTANT link or creates a channel access link if SIML type is PV_LINK. VAL is likewise initialized if SIOL is CONSTANT or PV_LINK.
This routine next checks to see that device support is available and a device support read routine is defined. If either does not exist, an error message is issued and processing is terminated
If device support includes init_record, it is called.
process
See next section.
get_value
Fills in the values of struct valueDes so that they refer to the array.
cvt_dbaddr
This is called by dbNameToAddr. It makes the dbAddr structure refer to the actual buffer holding the result.
get_array_info
Obtains values from the array referenced by VAL.
put_array_info
Writes values into the array referenced by VAL.
get_units
Retrieves EGU.
get_prec
Retrieves PREC if field is VAL field. Otherwise, calls recGblGetPrec().
get_graphic_double
Sets the upper display and lower display limits for a field. If the field is VAL the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.
get_control_double
Sets the upper control and the lower control limits for a field. If the field is VAL the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.
get_graphic_double
Sets the following values:
upper_disp_limit = HOPR lower_disp_limit = LOPR
get_control_double
Sets the following values
upper_ctrl_limit = HOPR lower_ctrl_limit = LOPR
Record Processing
Routine process implements the following algorithm:
- Check to see that the appropriate device support module exists. If it doesn't, an error message is issued and processing is terminated with the PACT field still set to TRUE. This ensures that processes will no longer be called for this record. Thus error storms will not occur.
- Call device support read routine.
- If PACT has been changed to TRUE, the device support read routine has started but has not completed writing the new value. In this case, the processing routine merely returns, leaving PACT TRUE.
- Check to see if monitors should be invoked.
- Alarm monitors are invoked if the alarm status or severity has changed.
- Archive and value change monitors are always invoked.
- NSEV and NSTA are reset to 0.
- Scan forward link if necessary, set PACT FALSE, and return.
Device Support
Fields Of Interest To Device Support
Each waveform record must have an associated set of device support routines. The primary responsibility of the device support routines is to obtain a new array value whenever read_wf is called. The device support routines are primarily interested in the following fields:
| Name | Summary | Description |
|---|---|---|
| PACT | Processing Active | See Fields Common to All Record Types for an explanation of these fields. |
| DPVT | Device Private | |
| NSEV | New Alarm Severity | |
| NSTA | New Alarm Status | |
| INP | Input Link | This field is used by the device support routines to locate its input. |
| RATE | Sampling Rate | Some device support modules may find this useful. |
| PTSS | Pre-trigger Samples | Some device support modules may find this useful. |
| NELM | Number Of Elements In Array | |
| FTVL | Field Type Of Value | This is DBF_STRING, ... , DBF_ENUM. The device support routine should check that this is correctly defined. |
| RARM | Rearm | When set to 1, the device will be rearmed. The device support routine should reset it to 0 when done. |
| BPTR | Holds Address of Array | |
| NORD | Number of Elements Read | Device support must set this value when it completes. |
| BUSY | Is device busy? |
Device Support Routines
Device support consists of the following routines:
report
report(FILE fp, paddr)
Not currently used.
init
init()
This routine is called once during IOC initialization.
init_record
init_record(precord)
This routine is optional. If provided, it is called by the record support init_record routine.
get_ioint_info
get_ioint_info(int cmd,struct dbCommon *precord,IOSCANPVT *ppvt)
This routine is called by the ioEventScan system each time the record is added or deleted from an I/O event scan list. cmd has the value (0,1) if the record is being (added to, deleted from) an I/O event list. It must be provided for any device type that can use the ioEvent scanner.
read_wf
read_wf(precord)
This routine must provide a new input value. It returns the following values:
- 0: Success.
- Other: Error.
Device Support For Soft Records
The Soft Channel device support module is provided to read values from other records and store them in arrays. If INP is a constant link, then read_wf does nothing. In this case, the record can be used to hold arrays written via dbPuts. If INP is a database or channel access link, the new array value is read from the link. NORD is set.
This module places a value directly in VAL.
If the INP link type is constant, then NORD is set to zero. If the INP link type is PV_LINK, then dbCaAddInlink is called by init_record.
read_wf calls recGblGetLinkValue which performs the following steps:
If the INP link type is CONSTANT recGblGetLinkValue does nothing.
If the INP link type is DB_LINK, then dbGetLink is called to obtain a new input value. If dbGetLink returns an error, a LINK_ALARM with a severity of INVALID_ALARM is raised.
If the INP link type is CA_LINK, then dbCaGetLink is called to obtain a new input value. If dbCaGetLink returns an error, a LINK_ALARM with a severity of INVALID_ALARM is raised.
NORD is set to the number of values returned and read_wf returns.
EPICS Record Reference Manual - 19 MAY 1998
