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memory-usage.rst

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Memory Usage Monitor

Authors: Aarón Cuevas López
Version: 1
IO:Frame Source, Register Access
ONIX ID:28
ONIX Hubs::ref:`pcie_host`

Description

The Memory Usage Monitor produces periodic samples that contain information about data buffer memory status. This device is useful for monitoring if frames are being cleared fast enough by the host PC to prevent real-time delays or overflows. Ideally, buffering should never be used and the memory usage should remain at 0.

Register Programming

Address Name Access Time of Effect POR Value Reset Action Description
0x00 ENABLE R/W On Reset Implementation dependent, see hub documentation None

The LSB is used to enable or disable the device data stream:

  • 0x0: data output disabled
  • 0x1: data output enabled
0x01 CLK_DIV R/W Immediate CLK_HZ / HB_HZ where HB_HZ is a implementation dependent default rate None Read frequency clock divider ratio. Minimum value is CLK_HZ / 10e6
0x02 CLK_HZ R N/A N/A None The frequency parameter, CLK_HZ, used in the calculation of CLK_DIV.
0x03 MEM_WORDS R N/A N/A None The total number of 32-bit words in memory.

Device To Host Data Frames

Each frame transmitted to the host is structured as follows:

.. wavedrom::

    {
        reg: [
          {bits: 64, name: "Acquisition Clock Counter", type: 0},
          {bits: 32, name: "Device Address", type: 0},
          {bits: 32, name: "Data Size", type: 0, attr: 12},

          {bits: 64, name: "Hub Clock Counter", type: 3},

          {bits: 32, name: "Number of 32-bit Memory Words Used", type: 4}

        ],
        config: {bits: 224, lanes: 7, vflip: true, hflip: true, fontsize: 11}
    }

Host To Device Data Frames

This device does not accept input frames. All write attempts will fail with an error.