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.

5.1 Low Level Register Interface 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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LSI 53C875A technical manual Scsi Scripts, Low Level Register Interface Mode