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GMVA Setups

Modified 13:37, 10 May 2016 by ubach | Page History

    Version as of 22:18, 22 Jul 2024

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    Setup for 4 Gbps

    ALMA Mode 4 Gbps

    For ALMA compatibilty the DBBC2 stations must observe in fullband PFB mode covering the full 512 MHz per polarisation in a single IF channel.

    DBBC2  setup

    It is recommended to restart the DBBC PFB control software, if it was used in another mode (SPOL or FLEX) before setting the fullband mode. Reprogramming might not be necessary. Of course reprogramming is required if the DDC mode was used before.

    The only option to be commanded is

    dbbcform=full

    The 2bit digitalization threshold is fixed in this mode and optimization of the bit statistics is done most easily by adjusting the input counts using the IFx commands. To check the bit statistics short recordings can be analyzed with m5bstate.

    All data from the last Core2Board (IFD) will be send to VSI1 and all from last-1 (IFC) to VSI2. There is no option to choose something else.

    FILA10G setup

    To combine the both VSI streams it is usually enough to set the Fila10G to:

    splitmode off
    inputselect vsi1-2
    vsi_samplerate 64000000
    reset 
    vdif_frame 2 2 8000
    reset

    However, this will join the two steams to a single 64 bit stream one after each other VSI1 bit 0-31 and VSI2 bit 32 to 61. The correlator expects to have alternating bits from channel 1 and 2. VSI1 bit 0+1, VSI2 bit2+3, ....

    This can be forced with the following changes of the channel permutation matrix:

    regwrite chan_perm 0 0x21200100
    regwrite chan_perm 1 0x23220302
    regwrite chan_perm 2 0x25240504
    regwrite chan_perm 3 0x27260706
    regwrite chan_perm 4 0x29280908
    regwrite chan_perm 5 0x2B2A0B0A
    regwrite chan_perm 6 0x2D2C0D0C
    regwrite chan_perm 7 0x2F2E0F0E
    regwrite chan_perm 8 0x31301110
    regwrite chan_perm 9 0x33321312
    regwrite chan_perm 10 0x35341514
    regwrite chan_perm 11 0x37361716
    regwrite chan_perm 12 0x39381918
    regwrite chan_perm 13 0x3B3A1B1A
    regwrite chan_perm 14 0x3D3C1D1C
    regwrite chan_perm 15 0x3F3E1F1E
    reset

    The mode has been succesfully tested at Effelsberg (details).