Avago Technologies LSI53C876E User Manual

Page 199

Block Move Instruction

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 Dword
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 field defines the instruction to execute as a
block move (MOVE).

Target Mode
In Target mode, the Opcode bit defines the following

operations:

These instructions perform the following steps:

1. The LSI53C876 verifies that it is connected to the

SCSI bus as a Target before executing this instruction.

2. The LSI53C876 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

LSI53C876 receives the first command byte and
decodes its SCSI Group Code.

Byte Count

Physical Data Address

OPC

Instruction Defined

MOVE

CHMOV