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.

00

Byte Count

 

 

 

Physical Data Address

 

 

OpCode

27

This 1-bit field defines the instruction to be executed as a block move (MOVE).

Target Mode

OPC Instruction Defined

0MOVE

1Reserved

These instructions perform the following steps:

1.The LSI53C810A verifies that it is connected to the SCSI bus as a Target before executing this instruction.

2.The LSI53C810A 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 LSI53C810A receives the first command byte and decodes its SCSI Group Code.

If the SCSI Group Code is either Group 0, Group 1, Group 2, or Group 5, then the LSI53C810A overwrites the DMA Byte Counter (DBC) register with the length of the Command Descriptor Block: 6, 10, or 12 bytes.

Block Move Instructions

6-9

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LSI 53C810A technical manual OpCode, Target Mode