Abstract: A two-dimensional command block queue includes a plurality of command blocks in a first linked list. One of the command blocks in a string is included in the first linked list. The string is delimited by only a tail pointer stored in a tail pointer list. Following dequeuing the string for processing, a pointer to the one command block of the string that was in the common queue is included in a string head pointer list. The tail pointer to the string is not changed in the tail pointer list following dequeuing of the string. This allows any new SCBs to be appended to the end of the string, while the string is being processed. This allows streaming of new SCBs to an I/O device that had previously been selected and is still connected to the host adapter.

Abstract: An overrun data handling circuit in a SCSI initiator and an overrun data handling method automatically handle Packetized SCSI Protocol data overruns. A multi-data channel host adapter includes the overrun data handling circuit that automatically handles data overruns for one data context in a Packetized SCSI Protocol data stream without damaging data for other data contexts, in the data stream, for which a data overrun has not occurred.

Abstract: To implement a RAID 1 transaction, an initiator sends a single command, i.e., either a single read command, or a single write command, over a common I/O bus to a primary target device. A mirror target device snoops the common I/O bus and upon detecting the single command directed to the primary target device, effectively performs in the same manner as if the command had been directed to the mirror target device. Hence, a single command is used to effectuate a mirrored transaction.

Abstract: A host adapter uses a scatter/gather list that includes a plurality of sections. Each section of the scatter/gather list can have any desired size. A link element in one section of the scatter/gather list is used to link to another section in the list. The link element has a format that is the same as the data elements that represent data segments in the list. Each element in the scatter/gather list includes an end-of-list flag and an end-of-section flag. When the end-of-list flag is set, the host adapter knows that the end-of-the scatter/gather list has been reached. When the end-of-section flag is set, the host adapter knows that an address to another section of the scatter/gather list is available.

Abstract: A method for supporting flow control by a SCSI initiator using a Packetized SCSI Protocol includes transmitting a data packet information unit in a Packetized SCSI Protocol Data Out phase. The SCSI initiator also receives a signal in said Packetized SCSI Protocol Data Out phase to indicate whether another data packet information unit is to be transmitted in said Packetized SCSI Protocol Data Out phase.

Abstract: An overrun data handling circuit in a SCSI initiator automatically handles Packetized SCSI Protocol data overruns. A multi-data channel host adapter includes the overrun data handling circuit that automatically handles data overruns for one data context in a Packetized SCSI Protocol data stream without damaging data for other data contexts, in the data stream, for which a data overrun has not occurred.

Abstract: A host adapter, which interfaces two I/O buses, caches data transferred from one I/O bus to another I/O bus in a data first-in-first-out (FIFO)/caching memory. In addition, when a target device on the another I/O bus is ready to receive the data, data is transferred from the data FIFO/caching memory even though not all of the data may be cached in that memory. Hence, data is concurrently transferred to and transferred from the data FIFO/caching memory. The data transfer to the target device is throttled if cached data is unavailable in the data FIFO/caching memory for transfer, e.g., the data cache is empty for the current context.

Abstract: To implement a RAID 1 transaction, an initiator sends a single command, i.e., either a single read command, or a single write command, over a common I/O bus to a primary target device. A mirror target device snoops the common I/O bus and upon detecting the single command directed to the primary target device, effectively performs in the same manner as if the command had been directed to the mirror target device. Hence, a single command is used to effectuate a mirrored transaction.

Abstract: A parallel SCSI host adapter uses an expanded SCB array for both non-Packetized and Packetized SCSI Protocols. The expanded SCB array is partitioned into a low page and a high page. SCBs for non-Packetized SCSI Protocol target devices that utilize a one-byte tag are stored in the low page and the storage site number is the tag. SCBs for Packetized SCSI Protocol target devices that utilize a multi-byte tag are stored on both the low page and the high page. For Packetized SCSI Protocol target devices, the two-bytes required to identify the page and the number of the storage site in the page are used as the tag. SCBs for Packetized SCSI Protocol target devices are stored in the low page only if there are no available storage sites in the high page.

Abstract: A two-dimensional command block queue includes a plurality of command blocks in a first linked list. One of the command blocks in a string is included in the first linked list. The string is delimited by only a tail pointer stored in a tail pointer list. Following dequeuing the string for processing, a pointer to the one command block of the string that was in the common queue is included in a string head pointer list. The tail pointer to the string is not changed in the tail pointer list following dequeuing of the string. This allows any new SCBs to be appended to the end of the string, while the string is being processed. This allows streaming of new SCBs to an I/O device that had previously been selected and is still connected to the host adapter.

Abstract: A single host adapter hardware I/O control block contains information used to specify a transfer of data from a host system to a first target device and in addition information that specifies whether the data is to be mirrored, and if so, optionally identifies a second target device on which the data is to be mirrored. After transferring the single hardware I/O control block to the host adapter integrated circuit, the host adapter integrated circuit determines whether the hardware I/O control block specifies a mirrored transaction. If a mirrored transaction is specified, the host adapter integrated circuit generates a second hardware I/O control block for the second target device using the information in the first hardware I/O control block. When the execution of both hardware I/O control blocks is complete, the host adapter integrated circuit provides a single completion notification to the host system.

Abstract: A single hardware I/O control block is used to efficiently abort a target I/O command for a target I/O device, e.g., one target I/O device in a plurality of target I/O devices. The abort command is included in the same hardware I/O control block that specified the target I/O command to be aborted. Execution of both the target I/O command and the abort command returns only one hardware I/O control block pointer and generates only one interrupt to a host system when both the target I/O command and the abort command are completed. All time relationships between the execution of the abort command and execution of the original target I/O command are supported. There are no holes where the abort command is lost or where the host system is advised of target I/O command completion prematurely, or is not advised of completion at all.

Abstract: A SCSI initiator system includes a Packetized SCSI Protocol hardware packet engine that automatically transmits Packetized SCSI protocol command blocks to a SCSI target with substantially zero latency between the transmission of adjacent command blocks. The packet engine operates independently of any other hardware circuits in the SCSI initiator that are capable of command management. The SCSI initiator system includes a target execution queue containing at least one hardware I/O control block for a SCSI target. The target execution queue is stored in a memory. The system also includes a Packetized SCSI Protocol hardware packet engine coupled to the target execution queue. The Packetized SCSI Protocol hardware packet engine generates Packetized SCSI Protocol packets using information in the at least one hardware I/O control block directly.

Abstract: A single host adapter hardware I/O control block contains information used to specify a transfer of data from a host system to a first target device and in addition information that specifies whether the data is to be mirrored, and if so, optionally identifies a second target device on which the data is to be mirrored. After transferring the single hardware I/O control block to the host adapter integrated circuit, the host adapter integrated circuit determines whether the hardware I/O control block specifies a mirrored transaction. If a mirrored transaction is specified, the host adapter integrated circuit generates a second hardware I/O control block for the second target device using the information in the first hardware I/O control block. When the execution of both hardware I/O control blocks is complete, the host adapter integrated circuit provides a single completion notification to the host system.

Abstract: A single host adapter hardware I/O control block contains information used to specify a transfer of data from a host system to a first target device and in addition information that specifies whether the data is to be mirrored, and if so, optionally identifies a second target device on which the data is to be mirrored. After transferring the single hardware I/O control block to the host adapter integrated circuit, the host adapter integrated circuit determines whether the hardware I/O control block specifies a mirrored transaction. If a mirrored transaction is specified, the host adapter integrated circuit generates a second hardware I/O control block for the second target device using the information in the first hardware I/O control block. When the execution of both hardware I/O control blocks is complete, the host adapter integrated circuit provides a single completion notification to the host system.

Abstract: A method for accessing hardware I/O control blocks, which are stored in an hardware I/O control block array, by a parallel SCSI host adapter addresses one page in a plurality of pages of the hardware I/O control block array for the parallel SCSI host adapter using a first portion of a hardware I/O control block array pointer in the parallel SCSI host adapter. The one page includes a plurality of storage sites for hardware I/O control blocks. A hardware I/O control block stored in the one page is addressed using a second portion of the hardware I/O control block array pointer in the parallel SCSI host adapter. Addressing the hardware I/O control block stored in the one page includes using a tag supplied by a reconnecting SCSI target as the second portion.

Abstract: A flow control method performed by a SCSI target includes receiving a data packet information unit in a Packetized SCSI Protocol Data Out phase. The SCSI target also generates a signal during said Packetized SCSI Protocol Data Out phase to indicate whether another data packet information unit is to be transmitted in said Packetized SCSI Protocol Data Out phase.

Abstract: A method for supporting data streaming by a SCSI initiator includes receiving a data packet information unit in a Packetized SCSI Protocol Data In phase. The SCSI initiator also receives a signal in said Packetized SCSI Protocol Data In phase to indicate whether a header packet information unit or another data packet information unit is to be received next in said Packetized SCSI Protocol Data In phase.

Abstract: A SCSI selective options message delay expander includes a capability for monitoring messages transferred between a first port and a second port of the expander, for delaying a pre-selected message, for modifying the delayed pre-selected message, and for storing information obtained from the delayed pre-selected message. The ability to change messages allows the expander to be used with SCSI initiators and/or SCSI target devices that have SCSI characteristics different from the SCSI characteristics of the expander.

Abstract: A parallel SCSI host adapter includes a SCSI bus port and a host I/O bus port. The parallel SCSI host adapter takes a snapshot of state data for a first data channel coupling the SCSI bus port to the host I/O bus port following receipt of a complete Packetized SCSI protocol information unit having a context from the SCSI bus port. Following the snapshot, another Packetized SCSI protocol information unit for the same context is transferred over the first data channel. Since the snapshot requires substantially no time delay relative to a time delay associated with saving the state data in a hardware I/O command block for the context, latency between the information units for the same context is minimized in the parallel SCSI host adapter.