Hardware Description
ComTec GmbH
3-6
When the software reads the actual count value during a running measurement all values are
simultanously transferred to readout registers. Thus, comparison of rates or values is easily
feasible and accurate at any time.
3.2.4. Time Base / Reference Clock
To derive the outstanding temperature and long-term stability the MPA4(T) is equipped with an
on-board ovenized crystal oscillator (OCXO). This OCXO stabilizes the 10 GHz PLL (phase
locked loop) synthesizer that clocks the TOF sampling circuitry.
The reference is a 10 MHz clock. Either the internal (on-board) or an external reference is
software selectable, see section 5.1.1. See in 8.2.3 for the signal impedance and amplitude.
Optionally (software selectable) a 20, 40 or 80 MHz input clock maybe used as well.
For highest stability and accuracy Rubidium disciplined oscillators or GPS controlled clock
generators are available.
D
Q
Edge
Detection
Pulse
Shape
&
COUNT_IN[x]
TIMER_MODE[x]
GO_IN
WATCH_GO[x]
D
Q
COMMON_GATE
GATE_ALL_POLARITY
GATE_ALL_ENABLE
COMMON_GATE_USE[x]
D
Q
GATE[x]
GATE_POLARITY[x]
GATE_ENABLE[x]
COUNT_ARM[x]
PRESET_REACHED[x]
count[x]
D
Q
LOAD_IN
LOAD_POLARITY
LOAD_ENABLE[x]
SOFTWARE_LOAD[x]
load[x]
D
Q
UP/DOWN_IN[y]
UP_POLARITY[y]
UP_DN_ENABLE[y]
up/down[y]
shared by all counters
*
**
*
not available for counters 2 & 3
*
**
x=1...8, y=2...3
AAA = Internal Signals
BBB = External Inputs
Legend:
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Fig. 3.5: 100MHz counters control logic