Avago Technologies LSI53C1010 - Manual (Page 199)

SCSI SCRIPTS Processors 9-1
Chapter 9
SCRIPTS Programming
Topics
This chapter presents general information for some of the programming
tasks that are often performed by SCRIPTS programs. For the most
up-to-date example code for many of these operations, please contact
LSI Logic technical support.
This chapter contains the following sections:
•
Section 9.1, “Scatter/Gather Operations,” page 9-1
•
Section 9.2, “Loopback Mode,” page 9-4
•
Section 9.3, “Byte Recovery on Target Disconnect,” page 9-9
•
Section 9.4, “Synchronous Negotiation and Transfer,” page 9-18
•
Section 9.5, “Interrupt Handling,” page 9-19
•
Section 9.6, “Migrating Existing Software to Ultra, Ultra2, and Ultra3
SCSI,” page 9-26
•
Section 9.7, “Using the SCRIPTS RAM,” page 9-30
9.1 Scatter/Gather Operations
You use scatter/gather to collect data that is scattered throughout
memory and must be transferred across the SCSI bus together. Memory
management units keep track of physical locations of user data that
cannot be stored contiguously. During an I/O request for a SCSI device
to fetch data, the memory management unit builds a gather table that
provides the addresses of all of the desired data. There may be several
entries, or pages, of data associated with a single transfer. Without
scatter/gather each entry is treated as an individual transfer, requiring a
processor interrupt and DMA setup.