Avago Technologies LSI53C825AE - Manual (Page 190)

5-6 SCSI SCRIPTS Instruction Set
5.3 Block Move Instructions
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 being moved onto
the SCSI bus, SIOM controls whether that data comes from I/O or
memory space. When data is being 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 this bit is one, 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 longword 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