EVIO Data Format


EVIO (Event IO) is the raw data format used by the DAQ event builder.  The structure of an EVIO file is a tree of banks, each of which has a header and a data payload. 

EVIO Data Types

Each EVIO bank has a data type a tag and a num. The type corresponds to the contents of the bank. 

0x0c,0x0d,0x0e,0x10,0x20,0x40Ncontainerthis is a bank that contains other banks
0x00, 0x014uint32_tunsigned integers
0x0b4intsigned integers
0x0fNcompound typeFADC (or other!) compound format.
0x061int8_t = charchar
0x071uint8_tunsigned char
0x052uint16_tunsigned short
0x0a8uint64_tunsigned long

Source: EVIO C++ code data parser.
Note: The 0x0f compound type data contains a string that tells you what the layout of the data is. See EVIO documentation. 

On the CLON machines, in the directory pointed to by $CLON_PARMS, is the file "clonbanks.xml", which contains the "dictionary" for the EVIO contents of various bank tags used in the data.

EVIO Event types - 2015 Data Set

The very top bank in an event tree is usually a container bank (0x10). The "tag" of this bank indicates the event type.  The event types used for the 2015 data set of HPS are listed below. Note that this is set by the DAQ configuration and is thus subject to change. Currently 16 - 32 are special event types, all others are "Physics" events. For physics events, the  number  is a bit encoded state of the trigger, with the high bit, bit 7, set. Thus physics events start at 128 and go up. The bit 6 encodes a "sync" event, which will contain scalers. 

Event type #NameNotes
17Pre StartIndicates the "pre-start" transition in the DAQ
18GoIndicates the user pressed "Go" on DAQ
19PauseIndicates the user pressed "Pause" on DAQ
20EndEnd of run marker event.
31EpicsEpics event - Slow controls data that is injected into the data stream.
Bit 7PhysicsPhysics events should have bit 7 set
Bit 6SyncSync events (containing scalers and trigger config) should have bit 6 set.
(Note: The 1st event in the run will be a sync event, but does not always have the sync bit set.)
Bit 5PulserThe pulser triggered the event.
Bit 4LED/CosmicLED or Cosmic trigger.
Bit 3Pairs 1Indicates a Pair1 trigger.
Bit 2Pairs 0Indicates a Pair0 trigger.
Bit 1Single 1Indicates a Single1 trigger.
Bit 0Single 0Indicates a Single0 trigger.

EVIO Banks - 2015 Data Set

Below is a list of the banks and tags used in the 2015 Engineering Run for HPS. Note that the bank numbers and tags used are chosen by the DAQ configuration, and are thus subject to change. 

Parent banktagtag hexNameNotes
event type 17170x11PrestartOnly bank in pre-start event
event type 18180x12GoOnly bank in go event
event type 311290x81EpicsEpics mother bank
|-576180xe112Epics headerEpics header bank
|-576200xe114Epics stringEpics string bank - contains the epics data in one long string of value-key pairs.
 576210xe115ScalersScaler banks
Physics event>128bit 7 setPhysics 
|-491520xc000Event ID 


Crate NameContentsTagTag Hex
hps11SSP, ECal Bottom Disc/TDCs/Scalers, RF FADC460x2e
hps12ECal Top & RF Disc/TDCs/Scalers580x3a


ECal Top FADC37


hps2ECal Bottom FADC, Faraday Cup Disc/Scalers390x27

Prestart Bank

IndexPrestart bank0x11 (17)
0start timeunix timestamp
1run number 
2file number 

GO Bank

IndexGO bank0x12 (18)
0start timeunix timestamp



Head Bank

indexHEAD bank0xe10F (57615)
0version number 
1run number 
2event number 
3event unix_time 
4event type 
5roc pattern 
6event classification17,18,20,etc
7Trigger bits 

Event ID Bank

indexEVENT ID bank0xc000 (49152)
0Event number 
1TI trigger bits? 
2Readout Statusshould be 0


Scaler Bank

indexScaler bank0xe115 (57621)
3gated faraday cup with "TDC" threshold 
19gated faraday cup with "TRG" threshold 
35ungated faraday cup with "TDC" threshold 
51ungated faraday cup with "TRG" threshold 
67gated clock 
68ungated clock 

EPICS Header Bank

indexEpics Header Bank0xe112 (57618)
1Run number 
2Sequence # 
3Time Stamp 


indexEpics Sting Bank0xe114 (57620)
0Epics StringSee details below
Epics nameMeaningNotes
MBSY2C_energyBeam energy according to Hall B BSY dipole "bus" 
Beam energy measured in Arc "x" ; e.g. ARC2:p
PSPECIRBCKPair Spectrometer Current Readback 
HPS:LS450_2:FIELDFrascati probe field 
HPS:LS450_1:FIELDPair Spectrometer probe field 
MTIRBCKFrascati Current Readback 
VCG2C212C21 Vacuum gauge pressure 
VCG2C21A2C21A Vacuum gauge pressure 
VCG2C24A2C24A Vacuum gauge pressure 
VCG2H00A2H00 Vacuum gauge pressure 
VCG2H01A2H01 Vacuum gauge pressure 
VCG2H02A2H02 Vacuum gauge pressure 
scaler_calc1Faraday cup current 
scalerS12bHPS-Left beam halo count 
scalerS13bHPS-Right beam halo count 
scalerS14bHPS-Top beam halo count 
scalerS15bHPS-SC beam halo count 
hallb_IPM2C21A_XPOSBeam position X at 2C21 
hallb_IPM2C21A_YPOSBeam position Y at 2C21 
hallb_IPM2C21A_CURCurrent at 2C21 
hallb_IPM2C24A_XPOSBeam position X at 2C24 
hallb_IPM2C24A_YPOSBeam position Y at 2C24 
hallb_IPM2C24A_CURCurrent at 2C24 
hallb_IPM2H00_XPOSBeam position X at 2H00 
hallb_IPM2H00_YPOSBeam position Y at 2H00 
hallb_IPM2H00_CURCurrent at 2H00 
hallb_IPM2H02_YPOSBeam position X at 2H02 
hallb_IPM2H02_XPOSBeam position Y at 2H02 



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