Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E
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3.4
SCSI pointers
The disc drive supports systems that use the pointer philosophy described in the following paragraphs.
Consider the system shown in Figure 3.4-1 in which an initiator and target communicate on the SCSI bus in
order to execute a command.
Function
Origin
Initiator
Path
Control
Initiator
Target
Path
Control
Target
Function
Execution
SCSI
Bus
Figure 3.4-1. Simplified SCSI system
The SCSI architecture provides for sets of pointers to be kept within each initiator Path Control area (see
Figure 3.4-1). These pointers are in sets of three pointers per set. The pointers in each set point to three
storage area sections in the initiator. The three sections contain the following information:
1.
A command from initiator to target.
2.
Status (from target) associated with the command.
3.
Data (to/from target) associated with the command.
Of these three-pointer sets there are two types:
1.
Current (active) pointers (one set per initiator only).
2.
Saved pointers (one or more sets per initiator, up to seven sets total).
The use of these two types of pointers is described in the following paragraphs.
