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1.5 Address frames
C141-C013 67
1.5.5.3 Connection responses
Table 1.25 lists the responses to an OPEN address frame being transmitted.
Table 1.25 Connection responses
Response Description
AIP Arbitration in progress. When an expander device is trying
to open a connection to the selected destination port, it
returns an AIP to the source phy. The source phy shall
reinitialize and restart its Open Timeout timer when it
receives an AIP. AIP is sent by an expander device while it
is internally arbitrating for access to an expander port.
OPEN_ACCEPT Connection request accepted. This is sent by the destination
phy.
OPEN_REJECT Connection request rejected. This is sent in response by the
destination phy or by an expander device.
OPEN address
frame
If the AIP primitive has been detected just before the OPEN
address frame, this indicates a top-priority connection
request, meaning that the OPEN_ACCEPT primitive or an
OPEN_REJECT primitive must be sent. If an AIP primitive
has not been detected yet, this indicates that two connection
requests have crossed over the physical link. At this time,
arbitration fairness is used to determine which request
should take priority.
BREAK The destination port or expander port may reply with
BREAK indicating the connection is not being established.
Open Timeout
timer expires
The source phy shall abort the connection request by
transmitting BREAK.
After an OPEN_REJECT (CONNECTION RATE NOT SUPPORTED) has been
received by a SAS TARG port, the SAS TARG device shall set the connection
rate for future requests for that I_T_L_Q nexus to:
a) the last value received in a connection request from the SAS INIT port;
b) 1,5 Gbps; or
c) the connection rate in effect when the command was received.
1.5.5.4 Arbitration fairness
SAS supports least-recently used arbitration fairness.
(This is a service equalization method that lowers the priority of the most recently
used device, that is to say, gives higher priority to devices that have been in the
wait state for a long period of time.)