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4.2.8 State Signal Input
The state signal has to be applied as a LVTTL (low voltage TTL) signal on 50Ohms to the “STATE IN“ (BNC
socket) of the TDC.
In addition, the value of the variable named “TimeTag” in the tdc_gpx3.ini file (depending on the software
version which is used) must be adapted for the state signal to be registered by the TDC.
The state signal input assumes values 0 or 1, depending on the given electronic level of the LVTTL signal
(low or high).
For the state input to be functioning the following variables in the tdc_gpx3.ini must be used:
TimeTag = 3
TimeTag = 4
TimeTag = 5
TimeTag = 6
;must be set for using the state input in combination with the ADC functionality and
the master reset input. The tag counting is switched off and any signal to the “TAG IN“
is ignored.
;corresponds to the setting of TimeTag = 3
;must be set for using the state input. Hereby the state input functions in combination
with the tag signal functioning as a timer, counting the internal 80MHz clock signal of
the FPGA. A signal on “TAG IN“ resets the timer to 0.
;must be set for using the state input. Hereby the state input functions in combination
with the tag signal functioning as a counter, counting the external LVTTL signal applied
to the “TAG IN“.
4.2.9 Shutter Signal Input
The shutter signal allows to prevent stop signals which belong to a specific start signal to be respected by
the TDC. Each time a new start signal is applied (independent if it is an external start signal or an internal
one), the TDC checks if the shutter signal is applied. In case it is applied (high level on the shutter input),
the TDC ignores all incoming stop signals which belong to that specific start signal, meaning all incoming
stop signals are ignored and not fed into the data stream until the next start signal arrives, at which point
the shutter signal is checked again. Independent on if the shutter signal is applied or not, each start signal
is counted by the start counter.
The shutter signal has to be applied as a LVTTL (low voltage TTL) signal on 50Ohms to the “SHUTTER IN“
(BNC socket) of the TDC.
Time-to-Digital-Converter Octa Channel TDC Manual | Surface Concept GmbH
