DSSI Concepts
B-5
Each DSSI bus has a limit of eight physical addresses: one, two, or three
adapters (KFMSA-BAs) and from one to seven ISEs (RF disks or TF tapes).
Each ISE has a controller in the physical (tape or disk) drive which uses
the mass storage protocol (MSCP) or tape MSCP.
Each connection has an initiator and a target node. Any node on the bus
can act as either an initiator or a target. The actual communications are
limited to two nodes at a time. Arbitration mechanisms accommodate mul-
tiple dialogues on the DSSI bus.
The ISE receives a complete packet of information requesting a task to be
done. The controller interprets the packet and performs the task without
any further communication from other DSSI nodes. The controller has a
command queue and handles access requests. It can start and monitor an
internal diagnostic, and provide status of the storage element.
