Avago Technologies LSI53C1010 - Manual (Page 32)

2-2 Programming with SCRIPTS
with SCRIPTS using only a few hundred lines of SCRIPTS code.
SCRIPTS are independent of the CPU, operating system, or system bus
being used, so they are portable across platforms.
Important: The SCRIPTS processor is not used in chip families
subsequent to the LSI53C1010 and LSI53C1010R.
2.2 SCRIPTS and the SCSI Bus Phases
One important advantage of SCSI SCRIPTS is that the SCRIPTS
language corresponds directly to SCSI protocol. In conjunction with the
high level language syntax, it provides an excellent vehicle to master the
complexity of SCSI. The one-to-one relationship between protocol
phases and SCRIPTS instructions means that SCRIPTS can be
customized to specific operations on the SCSI bus, and that SCSI
software development is simplified by using SCRIPTS. SCSI uses the
bus phases in the order shown in
Table 2.1 . This table also shows the
SCSI SCRIPTS instructions that correspond to the SCSI bus phases for
initiator and target roles.
Table 2.1 SCSI Protocol and SCRIPTS Instructions
Bus Phase Definition
SCRIPTS
Instruction
(Initiator role)
SCRIPTS
Instruction
(Target role)
Bus Free This phase indicates that the SCSI bus is available. N/A N/A
Arbitration This phase allows the initiator to gain control of the
SCSI bus. SELECT ATN RESELECT
Selection During this phase, the initiator selects a target
device to perform the desired function. The Attention
option notifies the target that upon successful
selection the initiator desires to send further
messages. SELECT ATN WAIT
SELECT
Reselection The target reselects with the initiator during this
phase. WAIT
RESELECT RESELECT
Message-Out During this phase, the initiator can send messages
to the target, such as queuing or error recovery
information. MOVE WHEN
MSG_OUT MOVE WITH
MSG_OUT