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4.2.6 Tag Signal Input
The tag input is an additional counter input for signal counting. The counter number is included into the
general data stream of the TDC. The tag signal has to be applied as a LVTTL (low voltage TTL) signal on
50Ohms to the “TAG IN“ (BNC socket) of the TDC.
In addition changes in the tdc_gpx3.ini file must be made for the tag signal to be registered by the TDC.
The corresponding entry in the tdc_gpx3.ini file is:
TimeTag = X
X is an integer value and must be one of the following values: 0, 1, 2, 3, 4, 5 or 6.
The default setting is 0
.
Each value represents a certain functionality, which is described below:
4.2.5 Start Frequency Divider
The maximum start frequency for the Octa Channel TDC is restricted to 9MHz. To cope with larger start
frequencies the Octa Channel TDC is equipped with an internal start frequency divider for external start
frequencies of up to 150MHz (this mode only works when using the external start input). Herewith the
frequency divider can operate with different dividing factors, which can be set within the software, to
always guarantee a start frequency of below 9MHz.
The frequency divider is switched on/off within the tdc_gpx3.ini file, in which also the dividing factors are
set.
The corresponding entry in the tdc_gpx3.ini file is:
Start_Divider = X
X is an integer value and must be one of the following values: 0, 2, 4, 8, 16 or 32. The value 1 is not allowed.
The default setting is 0
X = 0 switches off the start divider and leads to normal operation without dividing the start frequency.
The time histogram will appear X times in series, when using a dividing factor of X. This is due to the fact
that only each 1st start pulse out of a sequence of X start pulses will be accepted as start signal, while all
stop signals are detected. This leads to the multiple time histograms that appear sequentially in time. The
multiple histograms can be resorted to one single time histogram by a MODULO-operation during data
analysis.
Time-to-Digital-Converter Octa Channel TDC Manual | Surface Concept GmbH
