Bitfields for ASPI request flags:
Bit(s)	Description	)
 0	posting enabled
 1	linking enabled
 2	residual byte length reported in Data Allocation Length field
 3	transfer from SCSI target to host
 4	transfer from host to SCSI target
 5	scatter/gather
 7-6	reserved
Note:	no data is transferred if both bits 3 and 4 are set; if neither is
	  set, the direction is determined by the SCSI command
SeeAlso: #01454