SAS Gen5 Controller PACKET_SYNC for Scrambler Synchronization
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Solution Overview
Problem
In the context of Serial Attached SCSI (SAS) Gen5, there is a challenge with maintaining synchronization between the scrambler and descrambler in the initiator and target devices, leading to potential CRC errors due to loss of synchronization, especially when transitioning from SAS Gen4 to SAS Gen5 modes, where the synchronization timing and initialization differ significantly.
Innovation Solution
The implementation of a controller in the SAS Gen5 apparatus that transmits a PACKET_SYNC extended binary primitive to reinitialize and synchronize the scrambler and descrambler when CRC errors occur or timeouts are detected, ensuring consistent frame transmission and reception across different SAS modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scrambler is initialized on transmission of PACKET_SYNC in packet mode, then the synchronization between scrambler and descrambler can be established, but loss of synchronization may continue until PACKET_SYNC is exchanged again causing CRC errors in frames
Solution Approach 1:
The invention transmits PACKET_SYNC proactively at predetermined intervals or before frame transmission begins, rather than waiting for synchronization loss to occur. This preliminary action ensures the scrambler and descrambler remain synchronized, preventing CRC errors and maintaining continuous frame transmission without interruption.
2Reliability
If PACKET_SYNC is transmitted frequently to maintain synchronization, then CRC errors are prevented, but transmission overhead increases
Solution Approach 1:
The invention implements periodic transmission of PACKET_SYNC at predetermined intervals rather than continuous transmission. This periodic action maintains synchronization reliability while minimizing transmission overhead, as the sync primitive is sent only when necessary to refresh synchronization rather than continuously.
Solution Approach 2:
The invention transmits PACKET_SYNC selectively based on detected conditions (such as timeout or error detection) rather than uniformly at all times. This partial action approach ensures synchronization is maintained when needed while avoiding unnecessary transmissions during normal operation, reducing overall overhead.
Data Source
AI summary
According to one embodiment, an apparatus is capable of exchanging a frame with an external apparatus in a packet mode of serial attached small computer system interface (SAS). The apparatus includes a controller configured to transmit a frame to the external apparatus, and to transmit a PACKET_SYNC extended binary primitive to the external apparatus when the frame is not correctly received by the external apparatus.