BitFlow NEO-PCE-CLB, Hardware Reference Manual

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Trigger The Neon
NEO-11-2 BitFlow, Inc. Version G.5
11.2 Trigger
11.2.1 Trigger Input Types
There are four trigger inputs.
TRIGGER_TTL - Single ended TTL level trigger
TRIGGER_DIFF - Differential (LVDS) trigger
TRIGGER_OPTO - Optocoupled trigger (only on some modes)
FEN - The FEN signal on the CL1 connector. (only one some models)
The hardware trigger is enabled/disabled by the bit EN_TRIGGER. Only one input at a
time is active (the software trigger bit, SW_TRIG, is always active). The active trigger is
selected by the bitfield SEL_TRIG. The current level of these inputs can be read from
software by reading the bits RD_TRIG_DIFF, RD_TRIG_TTL, RD_TRIG_OPTO and RD_
FEN. The unselected triggers will have no effect on the board. However, they can be
used as general purpose inputs.
11.2.2 The Optocoupled Trigger
The opto-coupled trigger allows the acquisition circuitry to accept a trigger signal
without having a galvanic connection to the trigger source. This is mandatory in some
medical and industrial application. The trigger information is passed as a light pulse
from an on-board LED that is coupled to a receiving phototransistor. The LED and the
phototransistor are in the same package, a Sharp PC3H711. Figure 11-1 shows the
electrical diagram of the optocoupled trigger circuit and a suggested circuit for the
driver. The LED is driven by an open collector driver. The user must supply his +5V
power to the LED. Note that there is no galvanic connection between the user’s circuit
and the acquisition circuitry.