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Chapter 2. Setting up the software

__MYEVENTSEGMENT_H is not deﬁned, and the #ifndef is true. This causes __MYEVENTSEGMENT_H

to be deﬁned, which prevents subsequent inclusions from doing anything.

Ë Newer compilers deﬁne many of the standard classes, functions and constants inside of the std::

namespace. The spectrodaq.h header refers to these without explicitly qualifying them with the

namespace. If the std:: namespace exists, this directive asks the compiler to search it for

unqualiﬁed names (e.g cin could be resolved by std::cin).

Ì The class we are deﬁning MyEventSegment implements the services of a base class called

CEventSegment. Anything that reads out a chunk of the experiment is an event segment and must

be derived from the CEventSegment base class.

Í By convention, events are segmented in to packets. A packet is a leading word count, followed by

an word that identiﬁes the contents of the packet followed by the packet body. Packet identiﬁers are

maintained by Daniel Bazin, and the set of packet identiﬁers that have been currently assigned are

described at: http://groups.nscl.msu.edu/userinfo/daq/nscltags.html If you are creating a detector

system that will need its own tag contact <[email protected]> to get one assigned. The

m_MyPacket is member data for the class. It is a CDocumentedPacket. Documented packets do

the book-keeping associated with maintaining the packet structure as well as documenting their

presence in documentation records written at the beginning of the run.

Î The support software for the CAEN V685 ADC is itself a class: CAENcard. We will create an

object of this class in order to access the module. This pointer will be used to access the object and

hence the module.

Ï This line declares the constructor for MyEventSegment. A constructor is a function that is called

to initialize the data of an object when the object is being created (constructed).

Ð This line declares the destructor for MyEventSegment. A destructor is a function that is called

when an object of a class is being destroyed. Since we will be dynamically creating the CAENcard

pointed to by module, we must declare and implement a destructor to destroy that object when

objects of MyEventSegment are destroyed.

Ñ The Initialize member function is called whenever the run is about to become active. If

hardware or software requires initialization, it can be done here. This function will be called both

when a run is begun as well as when a run is resumed.

Ò The Clear member function is called when it is appropriate to clear any data that may have been

latched into the digitizers. This occurs at the beginning of a run and after each event is read out.

(10) The MaxSize member function is obsolete but must be deﬁned and implemented for compatiblity

with older software. In the past this returned the maximum number of words the event segment

would add to the event. Now it is never called.

(11) The Read member function is called in response to a trigger. This member must read the part of the

event that is managed by this event segment.

We will also create an implementation ﬁle: MyEventSegment.cpp. This ﬁle will implement the member

functions that were deﬁned by MyEventSegment.h above. The contents of this ﬁle are shown below:

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ADC 400F Handbuch Seite 13