chan_select HDL Worker

HDL implementation of a positional channel selection tap that extracts and batches one slot from a 16-sample interleaved frame stream.

Detail

The input stream carries 16-sample sample_op_e messages produced by the channelizer, decimate3, bd_x16, or cr_x16. Within each message the bin identity is determined by slot position (the word’s position within the message, 0..15), not by any embedded metadata tag.

Slot tracking: the pos counter (4-bit unsigned) is reset to zero whenever a SOM beat is seen. For SOM words (pos is implicitly 0) the worker checks whether sel = 0 and, if so, pushes the IQ word into the FIFO. For non-SOM words, pos is compared against sel after the increment that has been applied to it since the last SOM; the check (pos + 1) = sel is evaluated before the registered increment so that slot 1 is matched on the first non-SOM beat. The SOM-resync property means any input alignment error recovers cleanly on the next incoming SOM.

FIFO: 2048-deep × 32-bit array with ram_style="distributed", identical in structure to the FIFO in tag_select. The distributed-RAM attribute keeps the read path single-cycle and avoids BRAM output-register latency.

Output batching FSM (ostate):

• OS_IDLE: waits for the FIFO to reach BATCH (1024) samples, or for EOF with any remaining samples.

• OS_SEND: clocks FIFO words out one per cycle subject to output_in.ready back-pressure. SOM is asserted when send_rem = msg_len (first word); EOM when send_rem = 1 (last word).

• OS_EOF: asserts output_out.eof after the final batch completes.

The shared count register tracks FIFO occupancy and is updated by pulse variables do_wr and do_rd resolved within the same clock edge so that simultaneous push and pop are correctly counted.

All input is consumed unconditionally (input_out.take <= input_in.ready); the worker exerts no back-pressure upstream.

Latency: selected IQ words are buffered in the FIFO. Time from reception of a matching slot word to its appearance at the output depends on FIFO fill and downstream back-pressure, bounded by the 2048-entry FIFO depth.

Worker Properties

• 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: complex_short_timed_sample

  • Optional: False

Outputs:

• output

  • Protocol: complex_short_timed_sample

  • Optional: False

Worker Ports

Inputs:

• input:

  • Type: StreamInterface

  • Protocol: complex_short_timed_sample-prot

  • ClockDirection: in

  • Data width: 32

Outputs:

• output:

  • Type: StreamInterface

  • Protocol: complex_short_timed_sample-prot

  • Worker EOF: true

  • Clock: input

  • Data width: 32

Utilisation

Utilization reporting is not currently implemented.