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5.1 Low Level Register Interface Mode
Chapter 5
SCSI SCRIPTS
Instruction Set
The LSI53C875A contains a SCSI SCRIPTS processor that permits both
DMA and SCSI commands to be fetched from host memory or internal
SCRIPTS RAM. Algorithms written in SCSI SCRIPTS control the actions
of the SCSI and DMA cores. The SCRIPTS processor executes complex
SCSI bus sequences independently of the host CPU. This chapter
describes the SCSI SCRIPTS Instruction Set used to write these
algorithms. The following sections describe the benefits and use of SCSI
SCRIPTS Instructions.
Section 5.1, "Low Level Register Interface Mode"
Section 5.2, "High Level SCSI SCRIPTS Mode"
Section 5.3, "Block Move Instruction"
Section 5.4, "I/O Instruction"
Section 5.5, "Read/Write Instructions"
Section 5.6, "Transfer Control Instructions"
Section 5.7, "Memory Move Instructions"
Section 5.8, "Load and Store Instructions"
After power-up and initialization, the LSI53C875A can be operated in the
low level register interface mode or in the high level SCSI SCRIPTS
mode.
With the low level register interface mode, the user has access to the
DMA control logic and the SCSI bus control logic. An external processor
has access to the SCSI bus signals and the low level DMA signals, which
allows creation of complicated board level test algorithms. The low level
interface is useful for backward compatibility with SCSI devices that
LSI53C875A PCI to Ultra SCSI Controller
5-1
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