fifo_message HDL Worker

Detail

The typical operation is described below for the store_all_controls property set to false:

The implementation of the HDL worker consists of a data buffer FIFO and a message buffer FIFO. Providing that the buffers are not full, any valid data for the message is written into the data buffer before writing a metadata word into the message buffer. If the incoming message is a zero length message then the metadata is written immediately. The metadata word consists of the message opcode, byte enables of the last data word and the data length. If either of the buffers are full, back pressure will be applied to pause incoming messages until messages have been extracted out of the FIFO and the buffers are no longer full.

When the message buffer becomes not empty and no back pressure is applied on the output port, a single metadata word is read from it, and if the metadata length indicates it’s a zero length message it is sent straight to the output. If the metadata length indicates data is also present then, providing back pressure is not applied on the output port, it is read from the data buffer and fed to the output. All data bytes are fully data enabled until the last sample where the metadata byte_enable is used to validate the output data. The output opcode will be provided by the metadata opcode and the SOM, EOM, Valid and Give outputs will be generated. The EOF output will be de-asserted until both buffers are empty and will then follow the state of the EOF input. The process is then repeated until the message buffer and data buffer are both empty.

The fill levels and counts together with their clear inputs are connected directly to their respective data or message buffers. The empty signals from each of the buffers are monitored and the empty count is incremented each time both buffers are simultaneously empty, with a write to the empty_count property resetting the count.

If the store_all_controls property is set to true:

The operation is as described above but each byte_enable input word is stored together with each data word in the data buffer and, once extracted from the data buffer, is output directly rather than asserting all byte enables until the last one.

Worker Properties

• store_all_controls: When set to true, the component will store all input control signals. This will require increased resources.

  • Type: bool

  • Access:

    • Parameter: True

    • Writable: False

    • Initial: False

    • Volatile: False

    • Read back: False

  • Default value: None

• ocpi_buffer_size_output

  • Type: ushort

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: True

    • Volatile: False

    • Read back: False

  • Default value: 0

• ocpi_blocked_output

  • Type: ulong

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: False

    • Volatile: True

    • Read back: False

  • Default value: None

• ocpi_max_latency_output

  • Type: ushort

  • Access:

    • Parameter: True

    • Writable: False

    • Initial: False

    • Volatile: False

    • Read back: False

  • Default value: None

• ocpi_latency_output

  • Type: ushort

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: False

    • Volatile: True

    • Read back: False

  • Default value: None

• ocpi_messages_output

  • Type: ulong

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: False

    • Volatile: True

    • Read back: False

  • Default value: None

• ocpi_bytes_output

  • Type: ulong

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: False

    • Volatile: True

    • Read back: False

  • Default value: None

Worker Ports

Inputs:

• input

  • Protocol: None

  • Optional: False

Outputs:

• output

  • Protocol: None

  • Optional: False

Limitations

Although the worker can simultaneously consume and produce samples on its input and output ports, respectively, a full message (an EOM) has to have been received before any samples can be produced on the output. Therefore, data_depth must be set large enough to accept a maximum size input message.

Utilisation

Utilization reporting is not currently implemented.