User Manual: Agilent Acqiris 8-bit Digitizers Page 30 of 59
3.8. Special Front Panel Input and Output (U1071A-FAMILY & DC271-
FAMILY)
Connector Function
CLK IN 50 Ω External Reference or External Clock Input
I/O A User configurable (see below)
TR OUT Signal occurs after an accepted TRIGGER.
I/O B User configurable (see below)
The DC271-FAMILY uses MMCX connectors for these functions; the U1071A-FAMILY uses the MCX type. The
I/O A and I/O B signals are 3.3 V compatible CMOS. This means that, on input, low is < 0.7 V and high must be in
the range [1.7 V, 5.0 V]. An unconnected signal will be high. This definition ensures TTL compatibility. On output,
the low level will be in the range [0 V, 0.7 V] and the high level in the range [1.7 V, 3.3 V] for HiZ. The high level
output will typically give 0.8 V into 50 Ω. The I/O A or B connectors can be used for an Enable trigger input or the
following output signals: 10 MHz reference clock, Acquisition skipping to next segment, Acquisition is active,
Trigger is armed.
3.9. External Trigger Output (U1071A-FAMILY & DC271-FAMILY)
When the digitizer is ready to be triggered and a valid trigger signal occurs, a trigger output is generated for external
use. It is always available on the Front Panel Trigger Out MCX or MMCX connector. The pulse ends when the data
acquisition for the trigger in question is complete.
NOTE: The External Trigger Output functionality is implemented in the hardware. No Trigger Out signal occurs for
software-generated triggers such as those of the AUTO mode of AcqirisLive or through the use of the function
AcqrsD1_forceTrigger. However, AcqrsD1_forceTriggerEx does generate the signal.
Trigger Output Block diagram:
The output swing is 1.6 V (± 0.8 V) when
unloaded and 0.8 V when terminated on 50 Ω.
The rise and fall times are 2.5 ns typical. The
offset can be adjusted, by software control in the
range [–2.5 V, +2.5 V] unloaded, or [-1.25 V,
+1.25 V] into 50 Ω. The maximum output current
capability is ± 15 mA. As the output is retro-
terminated, it is possible to drive a 50 Ω line unterminated (HiZ) without loss of
Signal: 1.6V swing
0v centered
Offset: +/-2.5 V
G=1
50 Ohm
Trigger Out
performance.
For a TTL compatible signal, set the offset to 1.0 V and the swing at destination will be +0.2 to +1.8 V.
For an ECL compatible signal, terminated on 50 Ω to –1.2 V, set the offset to –1.2 V and the output will be in the
range [–0.8 V, –1.6 V]).
Alternatively, to reduce the current drawn from the digitizer, the terminations shown here can be used:
For the DC135/DC135HZ/DC140/DC140HZ/DC211/DC211A/DC241/DC241A/DC271/DC271A/DC271AR
modules, a standardized trigger out signal can also be routed to the PXI Bus Star Trigger line.
R
68
R
220
-5V
GND
Trigger
Out
W ith
Offset
-1.18V
R
68
R
220
+5V
ECL
Signal
TTL
signal
GND
Trigger Out
With
Offset
+1.18V
