EPICS Cheat Sheet

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Channel Access command-lines

Channel Access (CA) allows users to interact with Process Variables (PV):

caget - get the value of one of more PVs
caput - change the value of a PV
camonitor - monitor the value of one or more PVs
cainfo - print info about a PV, including which host is running the IOC


$ caget kmp3:m1.VAL
kmp3:m1.VAL            60
$ caget kmp3:m1.{DESC,RTYP,DTYP}
kmp3:m1.DESC           theta motor
kmp3:m1.RTYP           motor
kmp3:m1.DTYP           asynMotor

Noteworthy fields

A Process Variable (PV) is a the field from a record:

PV = record_name + . + field_name

Most common fields:

VAL - the default field (used if no field is specified in the vast majority of cases)
SCAN - determines when a record processes
NAME - the record name (helpful if records are aliased)
DESC - record description
RTYP - the record type
DTYP - the device support type (not meaningful for all record types)
DISP - disable puts (ca = channel access & pva = pv access) from outside the IOC (when non-zero); e.g. disable a motor from the motorx_all screen
DISV/DISA/SDIS - disable record processing internally
  • Record processing is disabled when DISA equals DISV (e.g. uses SDIS field to read in a value/mode, which will disable some control if a certain mode is active)
  • DISA is set to the value of the PV in the SDIS field, if it isn't empty
TPRO - trace processing: when set to 1 prints out all the records that get processed after the record is processed; used only for troubleshooting

Note: some of the fields of a record are actually record attributes (they return the same value for all instances of the record type; see https://epics.anl.gov/)

IOC shell commands

To connect to (disconnect from) the IOC shell, see here:

help [command] - shows available commands or syntax of specified command
dbpr record_name [0-9] - displays fields and values for a given record
dbl - lists all records in an IOC
dbl record_type - lists all records of a specific type in an IOC
dbl record_type "field_list" - lists specified fields (space-separated list) of records of a specific type in an IOC
dbpf pv_name value - change a PV’s value – analogous to caput
dbgf pv_name - read a PV’s value – analogous to caget
epicsEnvShow - prints environment variables
seqShow - shows running sequence programs
seqStop - stops a running sequence program