Often the modules are highly multiplexed 16 channels

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Unformatted text preview: rsion time-to-digital converters pulse generators charge measurement amplifiers delay generators • Frequently used in timing experiments, like nuclear physics: catch events in detector, generate signal, measure strength, etc. • Often the modules are highly multiplexed (16 channels per card common) Winter 2008 CAMAC crate (above) and inhabitants (right) including two custom modules, two commercial time-to-digital converters (TDCs) and the crate controller (note interface cable (50-pin SCSI-2 style) 17 Winter 2008 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 CAMAC features Example Interface: APOLLO • 16-bit (newer are 24-bit) data words • Full command cycle in 2 µs 8 Mbit/sec Mbit/sec • Look-At-Me (LAM) interrupts computer when some event happens • Commands follow N.A.F. sequence: slot number, address, function – – – – Lecture 11 • APOLLO is a lunar ranging apparatus that fires 20 laser pulses per second at a selected lunar reflector, measuring the time-of-flight of photons making the round trip • Besides the essential function of data collection and apparatus coordination, we wanted remote operation capability • We also required strict thermal control so address specific modules by name/position A and F values perform tasks that are defined by module A often refers to channel number on multiplexed device F might indicate a read, a write, a reset, or other action Winter 2008 18 19 Winter 2008 20 5 Computer Interface 02/21/2007 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 Catalog of APOLLO Interfaces RTD Readout Scheme • Uses a Linux PC (runs for a year at a time, no crashes) • Two GPIB devices – GPS-disciplined clock; actuated optics (mirror tilt, lens focus) • 4 RS-232 devices – motor that spins optic (8N1 @ 57600); laser control (8E1 @ 9600); CCD camera control (8N1 @ 115200); laser power meter (bolometer) (8N1 @ 9600) • CAMAC crate with two devices – TDC for 10 ps timing; custom module to control timing – another device sits passively in crate, no access to dataway • DAQ card for analog input, digital output – analog inputs for RTDs (temperature); flow meters; pulse energy; telescope tilt angle – digital outputs for relay control: turning devices on and off • Parallel port used for additional digital outputs for more relays Winter 2008 21 Winter 2008 22 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 Example Temperature Record Reading • Read 6.7.3; skim 6.7.5; read 6.7.7; 6.7.9 Winter 2008 Lecture 11 23 Winter 2008 24 6...
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