The PV Tree displays the hierarchical data flow between EPICS records. It displays the record types and their current values as well as severity/status. It attempts to reflect the data flow by traversing input links (INP, INPA, DOL, …).
The PV Tree has two modes:
- “Run” :
- In this mode it will always display the current value of each item in the tree.
- “Freeze on Alarm” :
- In this mode, updates pause as soon as the root item of the PV Tree goes into alarm.
Enter a name into the “PV” text box, and see what happens.
This tool uses the EPICS Channel Access or PV Access network protocols to read PVs. Note that there is a difference between EPICS records in an IOC and channels on the network. There is no way to query EPICS IOCs for their database information to determine the available “input” links.
Given a PV name
x, the PV tree attempts to read the channel
If the channel is indeed based on a record, it will report the record type.
The knowledge of which links to follow for each record type is
configured into the EPICS PV Tree application via the
This allows maintainers of site-specific settings to add support
for locally developed record types, or add certain output links to the
list of links that the PV tree should trace and display.
The Channel Access protocol adds another limitation to the PV tree operation,
because Channel Access strings are restricted to a length of 40 characters.
The PV tree can therefore not read the complete value of links when they exceed
40 characters. This results in long record names being truncated and then failing to
resolve. As a workaround, the PV tree can read a link
x.INP$ with a trailing dollar sign,
which causes the IOC to return the value as a byte waveform without length limitations.
This mode, however, is not supported by older IOCs and older CA gateways.
If your site only runs IOCs and gateways that support the
x.INP$ channel name syntax,
you can enable the
org.phoebus.applications.pvtree/read_long_fields=true option in the PV tree preferences.
If your site still runs older IOCs, you won’t be able to use the PV tree with them unless you