added new cdc

[Peter-Herrmann]

No description provided.

[Peter-Herrmann]

• While a transaction's grant is in flight, mask the req output.
• A transaction's grant starts when the req and gnt bits are high
  at the secondary port and no gnt is in flight, send a grant pulse.
• The receipt of a grant by the controller port must be pulse
  synchronized.
• Grant pulses sent by the secondary port must be separated by at least
  one clock cycle to enable edge detection on the pulse synchronizer.
• When the primary receives a grant pulse, it asserts gnt_ack until
  gnt_in_flight is de-asserted.
• The receipt of a grant acknowledgement by the secondary port must be
  pulse synchronized.
• A transaction's grant is completed when the secondary port receives
  acknowledgement that the grant was received.
• The delay between the controller port receiving a grant and the
  controller port receiving a grant ack must be at least as long as
  the pipeline delay of the req signal.
• Resets must be synchronized across clock domains