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Time-to-Digital Converter Octa Channel TDC Manual
The start input of the TDC cannot handle pulses which are arriving in a time interval
of smaller than 120ns (e.g. as produced by connecting/ disconnecting the start signal
during TDC operation). If two such subsequent pulses are applied to the start input of
the TDC, the device will still deliver results, but these results might contain wrong timing
information.
The maximum frequency for the start signal of 9MHz. Larger start pulse frequencies must
be divided down with an appropriate frequency divider (e.g. divider with factor of 16 for
80MHz start pulse frequency).
Note
The temporal resolution is influenced mainly by the quality of the start signal because
the TDC measures the time in a leading edge determination. Therefore, if the start signal
is varying in time, one needs to process it by means of a constant-fraction-discriminator
or similar external electronics components.
4.2.4 Device Synchronization Signal Input/Output
The data acquisition can be synchronized to an external signal for various measurement applications linked
to external devices. This device synchronization signal has to be applied as LVTTL signal to the “SYNC IN”
(BNC socket) of the TDC. This functionality is switched on/off within the tdc_gpx3.ini file.
The corresponding entry in the tdc_gpx3.ini file is:
Ext_trigger = X
X is either NO or YES.
The default setting is NO
.
The TDC ignores any external synchronization signals if “Ext_trigger” = NO. In case that “Ext_trigger” = YES
and the “Sync In” signal is not provided, the device will not come to operation at all.
The TDC provides always a LVTTL signal on the “SYNC OUT” BNC socket after the end of each acquisition,
independent on the setting of “Ext_trigger”.
The TDC holds an internal electronics, which provide the TDC start signal for further extended measurement
use. The “START OUT” (BNC socket) provides either the external start if applied or the internal start,
generated by the FPGA.
4.2.3 TDC Start Output
Note
Do not forget to save the ini file after any changes you make and restart the software. For
further information check the software manual.
Time-to-Digital-Converter Octa Channel TDC Manual | Surface Concept GmbH
