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being communicated with. Name changes may affect links and fanouts; to prevent loss
of functionality make sure any FLNK names are also changed.
Set/Get PVs
The “set” PVs allow the user to change an instrument’s state. The “get” PVs allow the
user to read the value without changing the instrument’s state. “get” PVs are also useful
for keeping the database up to date by scanning using the .SCAN parameter, and can
be chained to set PVs so they will notify the user of state changes. Setting a SCAN
parameter other than
Passive
on a set PV is not recommended as it will change the
parameter value.
For all read/write attributes, both a set and a get PV are provided. Default names
for these PVs begin with either ”set” or “get” to avoid identical names on multiple
PVs. Attributes which are only read or only write have a single PV with neither a
“get” nor a “set” in the default name.
FLNKs & Fanout PVs
Forward links chain PVs together so when a PV is processed, the PV named in its FLNK
field will also process. Normally, there is only one FLNK field in a PV. The instrument’s
default PV database comes with a set of FLNKs to ensure “get” PVs are processed
when the matching “set” PV is processed.
Fanout PVs consist of sets of forward links to other PVs. Fanouts are useful when a
series of commands needs to be run in order, repeatedly. Instead of creating a long
chain of forward links, fanouts provide the same functionality while maintaining a legible,
traceable PV file. A fanout PV can be an entry in any FLNK field, the same as other PVs
can. Their FLNKs can also link to other fanout PVs. The instrument’s default PV
database comes with a set of fanouts which allow for standard instrument coercion.
Example fanout from ztscopeM.pv:
file "$(EPICS_PV_PATH)/db/ztecfanout.template" {
pattern {NAME, SELM, LNK1, LNK2, LNK3, LNK4, LNK5, LNK6, SCAN}
{ztec:SweepFanout, All,
"ztec:getHorzPoints",
"ztec:HorzRate",
"ztec:HorzInterval",
"ztec:getHorzTime",
"",
"",
"Passive"}
...
}
Viewing the Current PV Database File
The current PV database file can be checked by using the webLXI interface, discussed
in the Instrument Configuration section above and in the
ZFind User’s Guide
.
Click on the “PV File” link on the EPICS Configuration webLXI page, or navigate a
browser straight to
http://<your instrument’s ip address>/ztec.pv
. Note whatever the
name of the uploaded PV database file, it will be reached with this “/ztec.pv” path
extension.