Waveform Record (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 record-specific fields are described below, grouped by functionality.
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.
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.
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.
Alarm Parameters
The waveform record has the alarm parameters common to all record types. Alarm Fields lists the fields related to alarms that are common to all record types.
Monitor Parameters
These parameters are used to determine when to send monitors placed on the VAL
field.
The APST and MPST fields are a menu with choices Always
and On Change
.
The default is Always
, thus monitors will normally be sent every time
the record processes.
Selecting On Change
causes a 32-bit hash of the VAL
field buffer to be calculated and compared with the previous hash value every
time the record processes; the monitor will only be sent if the hash is
different, indicating that the buffer has changed. Note that there is a small
chance that two different value buffers might result in the same hash value, so
for critical systems Always
may be a better choice, even though it re-sends
duplicate data.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
---|---|---|---|---|---|---|---|
APST |
Post Archive Monitors |
MENU waveformPOST |
Yes |
Yes |
Yes |
No |
|
MPST |
Post Value Monitors |
MENU waveformPOST |
Yes |
Yes |
Yes |
No |
|
HASH |
Hash of OnChange data. |
ULONG |
No |
Yes |
Yes |
No |
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 indicates the number of elements that were read into the array.
The BUSY field permits asynchronous device support to collect array elements
sequentially in multiple read cycles which may call the record’s process()
method many times before completing a read operation. Such a device would set
BUSY to TRUE along with setting PACT at the start of acquisition (it could also
set NORD to 0 and use it to keep track of how many elements have been received).
After receiving the last element the read_wf()
routine would clear BUSY which
informs the record’s process()
method that the read has finished. Note that
CA clients that perform gets of the VAL field can see partially filled arrays
when this type of device support is used, so the BUSY field is almost never used
today.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
---|---|---|---|---|---|---|---|
VAL |
Value |
Set by FTVL |
No |
Yes |
Yes |
Yes |
|
BPTR |
Buffer Pointer |
NOACCESS |
No |
No |
No |
No |
|
NORD |
Number elements read |
ULONG |
No |
Yes |
No |
No |
|
BUSY |
Busy Indicator |
SHORT |
No |
Yes |
No |
No |
Simulation Mode Parameters
The following fields are used to operate the record in simulation mode.
If SIMM (fetched through SIML) is YES, the record is put in SIMS severity and the value is fetched through SIOL. SSCN sets a different SCAN mechanism to use in simulation mode. SDLY sets a delay (in sec) that is used for asynchronous simulation processing.
See Input Simulation Fields for more information on simulation mode and its fields.
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
---|---|---|---|---|---|---|---|
SIML |
Simulation Mode Link |
INLINK |
Yes |
Yes |
Yes |
No |
|
SIMM |
Simulation Mode |
MENU menuYesNo |
No |
Yes |
Yes |
No |
|
SIOL |
Simulation Input Link |
INLINK |
Yes |
Yes |
Yes |
No |
|
SIMS |
Simulation Mode Severity |
MENU menuAlarmSevr |
Yes |
Yes |
Yes |
No |
|
SDLY |
Sim. Mode Async Delay |
DOUBLE |
Yes |
-1.0 |
Yes |
Yes |
No |
SSCN |
Sim. Mode Scan |
MENU menuScan |
Yes |
65535 |
Yes |
Yes |
No |
Record Support
Record Support Routines
init_record
static long init_record(waveformRecord *prec, int pass)
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
static long process(waveformRecord *prec)
See “Record Processing” section below.
cvt_dbaddr
static long cvt_dbaddr(DBADDR *paddr)
This is called by dbNameToAddr. It makes the dbAddr structure refer to the actual buffer holding the result.
get_array_info
static long get_array_info(DBADDR *paddr, long *no_elements, long *offset)
Obtains values from the array referenced by VAL.
put_array_info
static long put_array_info(DBADDR *paddr, long nNew)
Writes values into the array referenced by VAL.
get_units
static long get_units(DBADDR *paddr, char *units)
Retrieves EGU.
get_prec
static long get_precision(DBADDR *paddr, long *precision)
Retrieves PREC if field is VAL field. Otherwise, calls recGblGetPrec()
.
get_graphic_double
static long get_graphic_double(DBADDR *paddr, struct dbr_grDouble *pgd)
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.
Sets the following values:
upper_disp_limit = HOPR
lower_disp_limit = LOPR
get_control_double
static long get_control_double(DBADDR *paddr, struct dbr_ctrlDouble *pcd)
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.
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 invoked if APST or MPST are Always or if the result of the hash calculation is different.
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:
Field |
Summary |
Type |
DCT |
Default |
Read |
Write |
CA PP |
---|---|---|---|---|---|---|---|
PACT |
Record active |
UCHAR |
No |
Yes |
No |
No |
|
DPVT |
Device Private |
NOACCESS |
No |
No |
No |
No |
|
NSEV |
New Alarm Severity |
MENU menuAlarmSevr |
No |
Yes |
No |
No |
|
NSTA |
New Alarm Status |
MENU menuAlarmStat |
No |
Yes |
No |
No |
|
INP |
Input Specification |
INLINK |
Yes |
Yes |
Yes |
No |
|
NELM |
Number of Elements |
ULONG |
Yes |
1 |
Yes |
No |
No |
FTVL |
Field Type of Value |
MENU menuFtype |
Yes |
Yes |
No |
No |
|
RARM |
Rearm the waveform |
SHORT |
Yes |
Yes |
Yes |
Yes |
|
BPTR |
Buffer Pointer |
NOACCESS |
No |
No |
No |
No |
|
NORD |
Number elements read |
ULONG |
No |
Yes |
No |
No |
|
BUSY |
Busy Indicator |
SHORT |
No |
Yes |
No |
No |
Device Support Routines
Device support consists of the following routines:
report
long report(int level)
This optional routine is called by the IOC command dbior
and is passed the
report level that was requested by the user.
It should print a report on the state of the device support to stdout.
The level
parameter may be used to output increasingly more detailed
information at higher levels, or to select different types of information with
different levels.
Level zero should print no more than a small summary.
init
long init(int after)
This optional routine is called twice at IOC initialization time.
The first call happens before any of the init_record()
calls are made, with
the integer parameter after
set to 0.
The second call happens after all of the init_record()
calls have been made,
with after
set to 1.
init_record
long init_record(dbCommon *precord)
This routine is optional. If provided, it is called by the record support
init_record()
routine.
get_ioint_info
long get_ioint_info(int cmd, 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
long read_wf(waveformRecord *prec)
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 the VAL field. If INP is a constant link, then
read_wf()
does nothing. In this case, the record can be used to hold a fixed
set of data or array values written from elsewhere. If INP is a valid link, the
new array value is read from that link. NORD is set to the number of items
received.
If the INP link type is constant, VAL is set from it in the init_record()
routine and NORD is also set at that time.