Avago Technologies LSI53C825AE User Manual

Page 193

Block Move Instructions

5-9

SCRIPTS can directly execute operating system I/O data
structures, saving time at the beginning of an I/O
operation. The I/O data structure can begin on any
longword boundary and may cross system segment
boundaries.

There are two restrictions on the placement of pointer
data in system memory:

•

The eight bytes of data in the MOVE instruction must
be contiguous, as shown below, and

•

Indirect data fetches are not available during
execution of a Memory-to-Memory DMA operation.

OPC

Opcode

This 1-bit Opcode field defines the type of Block Move
(MOVE) Instruction to be performed in Target and Initiator
mode.

Target Mode

In Target mode, the Opcode bit defines the following
operations:

These instructions perform the following steps:

1. The LSI53C825A verifies that it is connected to the

SCSI bus as a Target before executing this instruction.

2. The LSI53C825A asserts the SCSI phase signals

(SMSG/, SC_D/, and SI_O/) as defined by the Phase
Field bits in the instruction.

3. If the instruction is for the command phase, the

LSI53C825A receives the first command byte and
decodes its SCSI Group Code.

Byte Count

Physical Data Address

OPC

Instruction Defined

MOVE

CHMOV