Ocean Optics Flame-S, User Manual

Page: 67 / 130

6: Technical Specifications
225-00000-000-11-201604 57
Triggering Modes
The Flame supports three triggering modes, (plus Normal mode), which are set with the Trigger
Mode command. Detailed information of each triggering mode follows. Also refer to the External
Triggering Options document located on our website at http://oceanoptics.com/wp-
content/uploads/External-Triggering-Options_Firmware3.0andAbove.pdf . The following
paragraphs describe these modes.
Normal
In the Normal (Free-run) mode, the spectrometer will acquire back-to-back spectra based on
the integration period specified. After the Integration Cycle completes, the data is read out of
the detector and written into an internal FIFO where it is available for reading. In parallel to
this read/write operation, another integration is occurring. If the data from the FIFO is
completely read before the parallel integration completes, a back-to-back operation will
occur. If the data is not read (FIFO Empty) in this time period, the FPGA will generate an Idle
Cycle which is equivalent to one integration period and the data from the detector is
discarded. After the Idle Cycle has completed, the FIFO Empty status is checked. If the FIFO is
empty and a new spectrum is requested by the software, a new acquisition will begin. If either
condition is false, additional Idle Cycles will be generated until both conditions are true.
For the Flame-S and Flame-T, this is also referred to as the nonbuffering mode because only
one spectrum is stored within the FPGA and not multiple spectra. In this scenario, ReadEnable
is generated by the software/firmware to initiate each new acquisition. Since only one spectrum
is stored at a time in the FPGA, a new integration cannot be started until the FIFO data has
been fully retrieved by the software.
External Synchronous Trigger Mode
In the External Synchronous Trigger mode, two external triggers are required to complete a
data acquisition. The first rising edge starts the integration period and the second rising edge
stops the integration and starts the next. Thus the integration time is the period between the
two external trigger pulses. After the integration period, the spectrum is retrieved and available
to the user. As in normal mode, no further spectra are acquired until the original spectrum is
read by the user.
External Hardware Level Trigger Mode
In the External Hardware Level Trigger mode, a rising edge detected by the spectrometer from
the External Trigger input starts the integration period specified through the software interface.
After the integration period, the spectrum is retrieved and is ready to be read by the user. As
long as the trigger level remains active in a logic one state, back-to-back acquisitions can occur,
as in the Normal mode, until the trigger transitions to an inactive level. As in normal mode, no
further spectra are acquired until the original spectrum is read by the user.
External Hardware Edge Trigger Mode
In the External Hardware Edge Trigger mode, a rising edge detected by the spectrometer from
the External Trigger input starts the integration period specified through the software interface.