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Block Move Instructions 6-9
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.
OpCode 27
This 1-bit field defines the instruction to be executed as
a block move (MOVE).
Target Mode
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.
00 Byte Count
Physical Data Address
OPC Instruction Defined
0MOVE
1 Reserved