Flush Inserter (flush_inserter)

Inserts a number of zero data samples when a flush message is received.

Design

Inserts a configurable number of data samples, with the value zero, when a message with the flush opcode is received. The message with a flush opcode is then forwarded on.

Implementation

When a message with a flush opcode is received, back pressure is applied to the input interface. A state machine is used to clock out a data message with flush_length samples with a value of zero. If flush_length is greater than MAX_MESSAGE_LENGTH_G then the flush message is split into messages with a maximum length of MAX_MESSAGE_LENGTH_G. Input back pressure is then removed and the message with a flush opcode passes onwards.

The component adds no delay to normal interface messages.

Interface

Generics

  • DATA_WIDTH_G (integer): Sets the width of the interface data signal.

  • OPCODE_WIDTH_G (integer): Sets the width of the interface opcode signal.

  • BYTE_ENABLE_WIDTH_G (integer): Sets the width of the interface byte enable signal.

  • MAX_MESSAGE_LENGTH_G (integer): Sets the maximum length of a data message. If flush_length is greater than this then the message is split into messages with a maximum length of MAX_MESSAGE_LENGTH_G.

  • FLUSH_OPCODE_G (std_logic_vector): Sets the value of the flush opcode.

  • DATA_OPCODE_G (std_logic_vector): Sets the value of the data opcode.

Ports

  • clk (std_logic), in: Clock. Inputs and outputs registered on rising edge.

  • reset (std_logic), in: Reset. Active high, synchronous with rising edge of clock.

  • flush_length (unsigned), in: Number of zeros that should be inserted when a flush is received.

  • take_in (std_logic), in: High when data is taken from the input interface.

  • take_out (std_logic), out: High when primitive can take incoming data.

  • input_som (std_logic), in: SOM signal from OpenCPI interface.

  • input_eom (std_logic), in: EOM signal from OpenCPI interface.

  • input_valid (std_logic), in: Valid signal from OpenCPI interface.

  • input_byte_enable (std_logic_vector, BYTE_ENABLE_WIDTH_G bits), in: Byte enable signal from OpenCPI interface.

  • input_opcode (std_logic_vector, OPCODE_WIDTH_G bits), in: Opcode signal from OpenCPI interface.

  • input_data (std_logic_vector, DATA_WIDTH_G bits), in: Data signal from OpenCPI interface.

  • input_ready (std_logic), in: Ready signal from OpenCPI interface.

  • output_som (std_logic), out: Output of SOM signal from input interface with flush inserted.

  • output_eom (std_logic), out: Output of EOM signal from input interface with flush inserted.

  • output_valid (std_logic), out: Output of valid signal from input interface with flush inserted.

  • output_byte_enable (std_logic_vector, BYTE_ENABLE_WIDTH_G bits), out: Output of byte enable signal from input interface with flush inserted.

  • output_opcode (std_logic_vector, OPCODE_WIDTH_G bits), out: Output of opcode signal from input interface with flush inserted.

  • output_data (std_logic_vector, DATA_WIDTH_G bits), out: Output of data signal from input interface with flush inserted.

  • output_ready (std_logic), out: Output of ready signal from input interface with flush inserted.

Dependencies

The dependencies to other elements in OpenCPI are:

  • None.

There is also a dependency on:

  • ieee.std_logic_1164

  • ieee.numeric_std

Limitations

Limitations of flush_inserter are:

  • None.