These are the original system specifications that were used for the
design. These were made in December 2010 and January 2011. Certain
features have been changed when designing the card in March 2011.
FMC Time to Digital Converter: FMC TDC 1ns 5cha
5 inputs, TTL with 50 Ohm termination. Made termination software
Time tags apply to rising edges of inputs. They are made of two
parts: 32 bits for the UTC second and as many bits as needed for the
fractional part within the second (will depend on final choice of
Implementation details: timebase from a local TCXO on FMC card
and needs calibration. Much better accuracy will be reached when
used on a White Rabbit enabled FMC carrier.
External inputs need to be protected against +15V pulses with a
pulse width of at least 10us @ 50Hz (with protection diodes if
SMC connectors for all inputs. Actually lemo connectors are
preferred by the main client (CERN's TE-ABT group), to be discussed.
Decided to use LEMO 00 connectors
Minimum input pulse width: 100 ns. Narrower pulses should be
A circular buffer will contain time tags for at least the last 100
input pulses. These time tags will at first be rough UTC (counter
initialized by SW) giving ~ms accuracy. Later, with a WR-enabled
solution, they can be much more accurate. Differences between
channels will not suffer from this accuracy problem because the
offset with respect to UTC will cancel.
Programmable (enable/disable) host interrupts on all 5 channels.
FMC mezzanine using a Low Pin Count (LPC) connector.