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1.6 Transport layer
C141-C013 83
• TAG field
The drive checks for duplication of tags. If a tag is found to be duplicated in
the SAS address of the port, the drive sends the ACK primitive to temporarily
close the connection. Then, after re-establishing a connection, the drive
reports the CHECK CONDITION status with the OVERLAPPED
COMMANDS DETECTS error. At this time, the drive aborts processing of
all the commands received from the SAS address of the port.
• CRC field
When a CRC error is detected, the drive sends the NAK primitive, and
discards the COMMAND frame.
• Frame length
When the IU length is other than 28 bytes, the drive reports INVALID
FRAME (Response Code=0x02).
• Command queue count value
If the drive receives a command when the queue is full, the drive sends the
ACK primitive to temporarily close the connection. Then, after re-
establishing a connection, the drive reports the QUEUE FULL status.
• LOGICAL UNIT NUMBER field
• TASK ATTRIBUTE field
• CDB field
Refer to Chapter 2, "Command Processing," and Chapter 4, "Command
Specification."
• Reserved field
The drive ignores the Reserved fields except the CDB field.
• Management of the command queue count (supplementary explanation)
The maximum command queue count (the upper limit of the number of commands
to be accepted) of a drive is 128. However, if the drive is a dual port drive and,
for example, has already queued 128 commands at port A, the drive can receive
another command at port B without causing the Queue full error. In other words,
at least one command can be received at each port of the drive even when the
drive is in the Queue full state.