Abstract: A system for sending large Command Descriptor Block (CDB) structures in a serial attached SCSI (SAS) controller includes a CDB Transmit Block, a CDB Memory, a Context Memory, a Direct Memory Access (DMA) Queue, a Transmit DMA Engine, and a SAS Interface. The CDB Transmit Block receives one or more Message Frames. If the CDB is small (32 bytes or less), the CDB Transmit Block reads data from the Message Frame and transmits a SAS Command Frame over the SAS interface. If the CDB is large (33 bytes or more), the CDB Transmit Block places a large CDB entry into the DMA Queue. The Transmit DMA Engine receives the large CDB entry from the DMA queue, utilizes an address pointer from the Message Frame to the CDB Memory to fetch large CDB information into a DMA buffer, and transmits a SAS Command Frame over the SAS interface.

Abstract: A system for sending large Command Descriptor Block (CDB) structures in a serial attached SCSI (SAS) controller includes a CDB Transmit Block, a CDB Memory, a Context Memory, a Direct Memory Access (DMA) Queue, a Transmit DMA Engine, and a SAS Interface. The CDB Transmit Block receives one or more Message Frames. If the CDB is small (32 bytes or less), the CDB Transmit Block reads data from the Message Frame and transmits a SAS Command Frame over the SAS interface. If the CDB is large (33 bytes or more), the CDB Transmit Block places a large CDB entry into the DMA Queue. The Transmit DMA Engine receives the large CDB entry from the DMA queue, utilizes an address pointer from the Message Frame to the CDB Memory to fetch large CDB information into a DMA buffer, and transmits a SAS Command Frame over the SAS interface.

Abstract: Methods and structures for opportunistically managing queued frames directed from a first SAS device to one of multiple other SAS devices coupled to the first device. A SAS application layer is coupled to a plurality of SAS transport layers through an arbitrated communication medium. Each transport layer is associated with a corresponding SAS device. Queued frames from the SAS application layer may be maintained in a per-device queuing structure associated with the SAS application layer. Upon receipt of an indication of readiness from the SAS transport layer that wins arbitration, a next SAS frame queued for the corresponding SAS device is unqueued and forwarded to the SAS device regardless of the number of other SAS frames queued for other SAS devices that lost the arbitration.

Abstract: Methods and structures for validating tag information received in SAS frames by any of a plurality of ports comprising a SAS wide port. Each port may have a dedicated transport layer processing element. A tag information table is shared by all of the one or more transport layer processing elements. The tag information table is used to store information regarding a particular tag value being valid for use with a particular device and is updated when the particular tag value is no longer valid for use with the particular device. The information is initially stored in response to transmission of a frame that first uses the particular tag value with the particular device. The tag information table is updated to indicate the particular tag value is no longer valid upon receipt of an appropriate SAS frame or by a processing element external to the one or more transport layer processing elements.