A Short Introduction to Data Acquisition Hardware

"Master" and "Slave" Digitizers

The digitizer modules may be used in pairs where one digitizer is labeled the “master” and the other is labeled the “slave”. In this configuration the two digitizers have different versions of firmware. The “master” digitizer alone connects to the trigger system. A ribbon cable connects the “master” digitizer to the “slave” digitizer. The “slave” digitizer channels are normally configured to use signals from the “master” digitizer as part of the logic determining if discriminators within the “slave” channels will fire or not, or whether events within the “slave” are marked for readout or not.

Clocking and Timestamps

The ADC chips run at a frequency of 100MHz (100 MSamp/sec). The device may run from its own internal oscillator or may receive a clock from an external trigger system and synchronize to that clock. A clock distribution from the trigger allows many digitizer modules to run synchronous to each other.

The digitizer module uses a 48-bit timestamp counter run from the 100MHz clock. When connected to the trigger system, the trigger may issue a command to synchronously reset the timestamp in all digitizers. Events read out of the digitizer are tagged with a timestamp for sorting and analysis.

Connection to External Trigger System

Digitizer modules may connect to a trigger system for synchronization and event selection purposes. A separate cable plant connects digitizer modules to trigger modules; on the digitizer end the cable uses the same RJ45 connector as Ethernet, but the signal levels and usage are not Ethernet. Do not connect the digitizer to an Ethernet port, this will damage the digitizer module.

The digitizer can run standalone without being connected to a trigger system. In this configuration every digitizer board has independent and unsynchronized clocks. Timestamps for event sorting are not useful across multiple modules as there is no synchronism, but within one board timestamps are still sensible.

See MyRIAD_USER_Manaual or MyRIAD_Abridged_User_Notes in Original Content prior to the ''Gammasphere Upgrade Project'' for detailed information on External Trigger systems.