TDC-GPX acam messelectronic gmbh, TDC-GPX Datasheet - Page 39

• Manufacturer Part Number: TDC-GPX
• Description: Precision Time Interval Measurement
• Manufacturer: acam messelectronic gmbh

Alutrigger
4.3 R-Mode Basics
In this mode the TDC-GPX offers:
Figure 30 Measurement timings
In this mode the TDC-GPX has two independent STOP
input channels, each one capable of measuring the
rising or falling. Each channel can store a minimum of
32 hits.
For improvement of the measurement accuracy, three
channels are internally combined, which leads to a
resolution of typical 27 ps. The trebled channels are
called combined channels. Each one of these combined
channels measures rising or falling edges of one sam-
pling channel. Two adjacent rising or falling edges on a
sampling channel may have a delay of down to 5.5 ns
(typ.).
Each STOP input has an 8 Bit stop counter, sensitive
to the rising edge. The number of hits for each input
can be read from register 11, StopCounter0 and
StopCounter1.
Parameter
EF
Start
Stop
t
2 Stop channels referring to 1 start channel
Each of 27 ps resolution
Start-retrigger up to 9 MHz
Rising or falling edge
5.5 ns pulse-pair resolution
0 to 40 µs measuring range
Minimum 32-fold multihit capability
Optional quiet mode
LVPECL inputs
t
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t
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ph
ss
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t
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acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
Time (Condition)
107 ns (max.)
*5.2 ns (min)
1.5 ns (min.)
1.5 ns (min.)
6.9 ns max.
40 µs (max.)
t
5.5 ns typ.
ph
0 ns (min)
t
ss
t
ph
#
t
Minimum pulse width
Minimum pulse width
Start to Stop
*with StopDisStart = 1
edge to edge
#
ALU start to data valid
pl
@ 87 ps resolution
t
rr
Description
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39
Internally the Start is shifted by an offset (in multiples
of LSB). This allows measuring hits that arrive earlier
than the start signal and to measure down to 0 ns.
Input circuitry
In R-Mode the TDC-GPX has differential low-voltage
PECL input buffers. The power for the differential in-
puts has to be switched on separately by setting regis-
ter 6, PowerOnECL = ‘1’.
The detailed input structure is shown in Figure 29.
Each input can be set to be sensitive to rising or falling
edge. This is done in register0, RiseEn0..2 and
FallEn0..2. A zero in both bits for one channel at the
same time disables the channel.
All inputs can be disabled by hardware, the stop inputs
separately for rising and falling edges (pin ‘StopDis1’
disables inputs DStop1,rising edge etc.).
They also can be disabled by software setting the ‘Dis-
able’ in register 2. The ‘Disable’ bits have to be set in
triples, e.g Disable3, Disable4 and Disable5 to disable
DStop1.
StopDisStart & StartDisStop
By default the Start and Stop inputs of the TDC-GPX
are open immediately after a reset.
The consequence for the Stop channels is that even
hits coming before a Start pulse will be measured. The
bit StopDisStart in register 5 disables the Stop chan-
nels until there is a Start pulse. A consequence is that
there is a minimum delay of 7 ns after the Start before
hits are accepted on the Stop channels.
With single-start only the first Start pulse is used for
the measurement. In case more than one Start pulse
is expected this might cause an overflow of the Hit
FIFO of the Start channel. This will produce garbage
data. There we recommend setting the StartDisStart
bit in register 5. A ‘1’ disables the Start channel after
the first Start pulse.
External Start Retrigger
A further option is to retrigger the Start externally.
This option is activated by setting StartRetrig = 1 (Reg
5). The maximum retrigger frequency is limited to
typically 9 MHz. Higher rates will disturb the chip.
TDC-GPX