Flag Name and FunctionREC Error RecoveryThis flag (bit 14) is used by the host to perform error recovery procedures while theassociated target is in a state of extended contingent allegiance. A state of extendedcontingent allegiance exists as long as the host adapter returns this status (StatusWord 1, bit 14) in the status block. The condition is cleared by issuing a Resumeimmediate command.If this bit is set to one, and the target is in a state of extended contingent allegiance,the host adapter will execute the command. If the target is not in a state ofextended contingent allegiance, the host adapter will reject the control block andreport a specification check. The control blocks will also be rejected with aspecification check if the Tagged Queuing flag (bit 3) is set.If this bit is set to zero, and the target is in a state of extended contingentallegiance, the host adapter will accept the command but not execute it until thecondition is cleared. If the target is not in a state of extended contingent allegiance,the control block will be executed normally.This option has been defined for future versions of SCSI-2 subsystems. For currentversions, this flag should always be set to zero.NRB No Retry on Busy StatusThis flag (bit 15) determines whether or not the host adapter will automaticallyretry an Initiator SCSI Command if the target returns Busy status.If this bit is set to one, the host adapter will terminate the command upon detectingbusy status from the target. The host will be notified that the command completedwith error. The target status field in the status block (byte 03) will reflect that aBusy status code (08h) was returned.If this bit is set to zero and the target returns busy status, the host adapter willretry the command indefinitely until the target completes the command successfullyor until the command is aborted by the host via an Immediate command.Data or Scatter/Gather List PointerThis 32-bit field contains the physical memory address (least significant byte first) ofthe first byte of the host memory data area to be used during the data phase of theSCSI command.If the Scatter/Gather flag (Flag Word 1, bit 12) is set to one, this field contains thephysical address of the first byte of list of data pointers and lengths to be used duringthe data phase of the SCSI command. The number of 8-byte segments is limited to128 (one pointer and one length), but the host adapter will only store a maximum of17 segments in its internal memory at a time. The diagram below describes the struc-ture of the Scatter/Gather list.adaptec AHA-1740A/1742A/17446-10
