From tigwiki

[edit] Caveat

Last updated 2 August 2005.  This particular section of the acquisition is seriously in flux.  If something doesn't make sense, it may be that this document has not been updated to properly reflect what's going on.

[edit] What they are

There are three sets of scalers to deal with here.  One set isrefered to as the "scalers".  This is a bank of three Lecroy 4434 32-channel scaler modules.  They are read out and cleared at all run transitions, and either periodically or when the Jorway sequencer raises a LAM.  In either case the data goes into the SCLR bank of the Midas format in either Camac or Scaler events.  The exact locations are defined in 8pi.c, but to keep things simple, the leftmost 4434 houses the first 32 channels and the rightmost 4434 houses the last 32 for a total of 96 channels.

The second set is a <A HREF="#MCS">Multichannel Scaler</A> SIS 3801, http://daq-plone.triumf.ca/HR/VME/SiS/sis3801v56.pdf/view, VME module.  Its data goes into the MCS0 bank.  It is read out at the same time as the Lecroys.

The third set of "independent scalers" or "i-scalers" #IScalers is a Lecroy 2551 12-channel scaler, described below.

[edit] How they are defined

Any that aren't listed here, aren't defined and should be zero.  These can be found in /Equipment/Scalers/Variables/SCLR.

[edit] When are the scalers enabled or disabled

The Scaler equipment is enabled or disabled by the ODB entry /Equipment/Scaler/Common/Enabled, http://isdaq08.triumf.ca:8081/Equipment/Scaler/Common/Enabled?cmd=Set&exp=8pi. This is normally automatically taken care of by the front-end code; i.e. the scalers will be disabled at the start of a cycle-mode run, and are enabled at all other times.  If you accidentally change the enable/disable status of Scales in the middle of a run, the contents of the scalers -- whether read out as a Scaler event or a Camac event -- will be unreliable, or at least difficult to interpret.

[edit] The Multichannel Scaler

The <A HREF="http://daq-plone.triumf.ca/HR/VME/SiS/sis3801v56.pdf/view">SIS 3801 Multichannel Scaler</A> counts the scintillators per timeslice.  It is read out every time the "scalers" are read out, as determined by the status of /Equipment/Scaler/Common/Enabled, http://isdaq08.triumf.ca:8081/Equipment/Scaler/Common/Enabled?cmd=Set&exp=8pi and /Equipment/Camac/Settings/Jorway/CycleEnable, http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Jorway/Cycle%20Enable?cmd=Set&exp=8pi. The MCS has some control ODB entries in /Equipment/Scaler/Settings/MCS0 http://isdaq08.triumf.ca:8081/Equipment/Scaler/Settings/MCS0?exp=8pi. Its contents are dumped into the same event as the "scalers".

The MCS is set up to take an external clock, and in the 8pi implementation we are using Paul Garrett's 10 MHz clock.  The Prescale entry sets the width of each time slice on the MCS as that number, plus one, times the period of the clock.  For example a Prescale setting of 999,999 means 1,000,000 clock ticks per time slice, that is, 0.1 seconds per time slice. The Slice Enable entry determines whether or not you will use the MCS as a time-divided MCS, or as a simple scaler just like the Lecroy 4413s.  The Channels entry says, read out only the first so-many input channels from the MCS.  

NOTES AND GOTHCAS:  

• For reasons none of us fully understand, on these 3801 MCSs,  you can only read out 24 or less channels, or all 32.  If you can figure it out, tell us.  There is also annecdotal evidence that you can only set the MCS to read out multiples of four channels.
• If you change Channels here you will have to modify the analyzer code and recompile it.
• Even though this module *should* be able to handle it, we have had trouble when the counting time (i.e. total cycling program time, Setting up Beam, Tape & Trigger Enable sequences and cycles) and prescale factor are set to give you much more than about 250 slices per cycle.

[edit] IScalers

The I-scalers, or "independent scalers", are the 12 channels of a single Lecroy 2551 scaler module.  It is read out independently every second or so, regardless of run status.  This data goes into an ISCL bank in IScaler events (type 4).  The IScaler equipment is typically set up to run indpendently every second regardless of run status.  It is especially useful for sending to EPICS so that e.g. Pierre can use it for tuning.  They should always be enabled.  Each IScaler event also contains a LIVE bank which is a number modulo 16 that is simply updated each time an IScaler event happens.  These i-scalers were implemented to provide a means of monitoring rates rapidly and independently of experimental conditions such as cycling modes, in particular so that they could be monitored by ISAC accelerator scientists to optimize our yield.  See the EPICS interface section for more details.

Configuration in August 2005.  IF IN DOUBT, TRACE CABLES.