Gaps - 1.2 English

Versal ACAP Integrated 600G Interlaken with FEC Subsystem Product Guide (PG371)

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1.2 English

The purpose of the segmented AXI4-Stream bus is to provide a means to optimally use the data bus. Therefore, ideally segments should be filled in sequence with no gaps between used segments. A “gap” on the TX AXI4-Stream bus is a disabled segment (that is, tx_axis_tuser_ena<M>=0).

All segments of the bus can be IDLE, or one or more segments (potentially to the last segment of the bus) can be disabled under the following conditions:

  • After a segment that results in a burst of size BurstMax
  • After a segment containing EOP
  • After a non-EOP segment that results in a burst of size < BurstMax (and > 64B)

The transmit logic of the ILKNF subsystem never violates the BurstShort value specified by c0_ctl_tx_burstshort register field of the CFG_C0_TX_MAIN_REG register. However, the core might inject more than the absolute minimum required number of IDLE Control Words depending on the burst size and on which segment the burst ends.