Jumps in hi res data



  • hi-res mode.
    • When the digital low pass filter in the fpga is enabled. It is used whenever the bandwidth is reduced from 172Mhz.
  • "sp":
    • code in fpga that does the spectral computations: (dlpf,pfb,fft, power,accumulation).
  • pncode:
    • pseudo noise code generated in the fpga. This data is then sent directly out of the fpga. It does not pass thru the "sp" fpga code
  • fpga,spectrometer,fileserver:
    • The mock spectrometer consists of a mock box (fpga, powerpc (ppc) spectrometer) connected to a file server
    • The fpga contains the pncode and sp code. It inputs the data, computes the spectra and outputs to the ppc (which runs in the mock box.
    • spectrometer: this usually refers to the ppc code running on the mock box (the prun program). It inputs data from the fpga and sends it to the file server.
    • the file server connects to the mock box via gigabit ethernet.
  • pnet,prun,psrv Programs:
    • pnet runs on a fileserver and controls all of the mock spectrometers in use.
    • prun runs on the power pc in the mock box. It controls the fpga. Pnet talks to prun.
    • psrv runs on the files server. It gets the data from prun and either verifies the data or writes it to disc.
    • normally refers to the power pc portion of the mock box. The fpga sends data to spectrometer which passes it on to the file server:


    The mock spectrometer has occasionally had bit flipping errors when running in high resolution mode (when the bandwidth is reduced from the clock frequency using the digital filter). The errors show up as single channel spikes in the spectra with sizes that are a power of 2 larger or smaller than adjacent values.
    The Mock diagnostics show that the problem only occurs when the fpga computes the spectra. The jumps are not seen when pure i/o tests are done from the spectrometer to the fileserver.
    The errors are intermittent.  They will remain for a few hours and then disappear.

    The rdcomp diagnostic is used to test for the error:

Examples of when this problem has occurred.

Summary of the problem and how to avoid it:

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