Eof (End Of Frame); Nak (Negative Acknowledgement); Rrdy; Sof (Start Of Frame) - Fujitsu MAU3147RC SERIES Technical Manual

Serial Attached SCSI (SAS) Interface
Meanwhile, when a drive receives the DONE primitive, the drive performs the
following processing:
1) If the drive has SSP frames to send at the time of the receipt of the DONE
primitive from the initiator, the drive can send as many SSP frames as there
are credits being held at this time.
2) If the drive has no SSP frames to send at the time of the receipt of the DONE
primitive from the initiator, the drive sends the DONE (NORMAL) primitive.
The side that has sent the DONE primitive cannot send the SSP primitive until
connection is established again after the current connection is temporarily closed.
1.4.4.4

EOF (End of frame)

EOF specifies the end of an SSP or SMP frame.
1.4.4.5

NAK (negative acknowledgement)

The NAK primitive indicates that an SSP frame cannot be received normally.
When a drive receives an SSP frame, and the drive detects a CRC error after
checking the CRC field in the SSP frame, the drive sends the NAK primitive.
If a received SSP frame contains the ERROR primitive or an invalid dword, the
drive sends the NAK primitive even if the CRC field in the SSP field is correct.
1.4.4.6

RRDY

During connection, when a drive detects the state where it can receive an SSP
frame, the drive sends an RRDY primitive to indicate that the connecting
companion can send the SSP frame. According to the ANSI specifications, the
sender of the OPEN_ACCEPT primitive must provide at least one RRDY
primitive within 1 ms.
When the OPEN_ACCEPT primitive is transferred, the maximum number of
RRDY primitives to be sent by a drive is as follows:
•
For a single port drive: four
•
For a dual port drive: three
The sending side of the SSP frame cannot send the SSP frame before sending
RRDY primitives (before the sending side obtains credits). If a drive receives
more SSP frames than the RRDY primitives it has sent, the drive discards the
surplus SSP frames.
1.4.4.7

SOF (Start of frame)

SOF specifies the start of an SSP or SMP frame.
1-36 C141-C009