MIDAS Event Construction

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MIDAS event construction

The MIDAS Event Structure is a variable length event format. It uses banks as subsets of an event.

Usually a bank contains an array of values that logically belong together. For example, an experiment can generate an ADC bank, a TDC bank and a bank with trigger information. The length of a bank can vary from one event to another due to zero suppression from the hardware. Besides the variable data length support of the bank structure, another main advantage is the possibility for the analyzer to add more (calculated) banks during the analysis process to the event in process. After the first analysis stage, the event can contain in addition to the the raw ADC bank, a bank with calibrated ADC values called CADC for example. In this CADC bank the raw ADC values could be offset or gain-corrected.

Midas Data Types Midas defines its own data types for OS compatibility. It is suggested that you use them in order to ensure correct compilation when moving code from one OS to another.

\em float and \em double retain OS definition.

- BYTE unsigned char - WORD unsigned short int (16bits word) - DWORD unsigned 32bits word - INT signed 32bits word - BOOL OS dependent.

When defining a data type either in the frontend code for bank definition or in user code to define ODB variables, Midas requires the use of its own data type declaration. The list below shows the main Type IDentification to be used (refer to @ref mdefineh for complete listing):

- TID_BYTE unsigned byte 0 255 - TID_SBYTE signed BYTE -128 127 - TID_CHAR single character 0 255 - TID_WORD two BYTE 0 65535 - TID_SHORT signed WORD -32768 32767 - TID_DWORD four bytes 0 2**32-1 - TID_INT signed DWORD -2**31 2**31-1 - TID_BOOL four bytes bool 0 1 - TID_FLOAT four bytes float format - TID_DOUBLE eight bytes float format

\anchor idx_Midas_bank @subsection FE_creation_Midas_banks Creation of MIDAS banks

MIDAS banks are created in the frontend readout code with calls to the MIDAS library. The following routines are available: - bk_init() , bk_init32() Initializes a bank structure in an event.

Note that bk_init32 can be used to reduce the size of very large banks, where the data will fit into a 32-bit word

- bk_create() Creates a bank with a given name (exactly four characters) - bk_close() Closes a bank previously opened with bk_create(). - bk_locate() Locates a bank within an event by its name. - bk_iterate() Returns bank and data pointers to each bank in the event. - bk_list() Constructs a string with all the banks' names in the event. - bk_size() Returns the size in bytes of all banks including the bank headers in an event.