What is exact meaning of sync for CHI SACTIVE signal

In the section "B14.7.1 Introduction" in IHI0050 - G AMBA® CHI Architecture Specification,

It says "SACTIVE signals must be synchronous to CLK and therefore are not required to be synchronized. If they cross a
clock domain, the clock domain crossing bridge is required to synchronize the signals."

I am not sure If It says SACTIVE must be aligned with FLITs or It just has to be synchronous signal which does not consider cycle accuracy  thoroughly.

Could you please more elaborate on the meaning of synchronous in the sentence? 

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  • This statement only means that the receiving interface should not be expected to have to synchronise SACTIVE - if it needs synchronisation, this would be done externally.

    The timing relationship is separate from this.  For example:

    • TXSACTIVE must be asserted before or in the same cycle in which the first flit relating to a transaction is sent.

    • TXSACTIVE must remain asserted until after the last flit relating to all transactions is sent or received.

Reply
  • This statement only means that the receiving interface should not be expected to have to synchronise SACTIVE - if it needs synchronisation, this would be done externally.

    The timing relationship is separate from this.  For example:

    • TXSACTIVE must be asserted before or in the same cycle in which the first flit relating to a transaction is sent.

    • TXSACTIVE must remain asserted until after the last flit relating to all transactions is sent or received.

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