Avago Technologies LSI53C876E - Manual (Page 196)

5-6 SCSI SCRIPTS Instruction Set
5.3 Block Move Instruction
Performing a Block Move instruction, bit 5, Source I/O - Memory Enable
(SIOM) and bit 4, Destination I/O - Memory Enable (DIOM) in the
DMA
Mode (DMODE) register determines whether the source/destination
address resides in memory or I/O space. When data is moved onto the
SCSI bus, SIOM controls whether that data comes from I/O or memory
space. When data is moved off of the SCSI bus, DIOM controls whether
that data goes to I/O or memory space.
5.3.1 First Dword
IT[1:0] Instruction Type - Block Move [31:30]
IA Indirect Addressing 29
When this bit is cleared, user data is moved to or from
the 32-bit data start address for the Block Move
instruction. The value is loaded into the chip’s address
register and incremented as data is transferred. The
address of the data to move is in the second Dword of
this instruction.
When set, the 32-bit user data start address for the Block
Move is the address of a pointer to the actual data buffer
address. The value at the 32-bit start address is loaded
into the chip’s
DMA Next Address (DNAD) register using
a third Dword fetch (4-byte transfer across the host
computer bus).
Direct Addressing
The byte count and absolute address are:
Indirect Addressing
Use the fetched byte count, but fetch the data address
from the address in the instruction.
Command Byte Count
Address of Data
Command Byte Count
Address of Pointer to Data