Avago Technologies LSI53C895A User Manual
Page 229
Block Move Instruction
5-7
Once the data pointer address is loaded, it is executed
as when the chip operates in the direct mode. This
indirect feature allows a table of data buffer addresses to
be specified. Using the LSI Logic SCSI SCRIPTS
assembler, the table offset is placed in the script at
compile time. Then at the actual data transfer time, the
offsets are added to the base address of the data
address table by the external processor. The logical I/O
driver builds a structure of addresses for an I/O rather
than treating each address individually. This feature
makes it possible to locate SCSI SCRIPTS in a PROM.
Note:
Do not use indirect and table indirect addressing
simultaneously; use only one addressing method at a time.
TIA
Table Indirect
28
32-Bit Addressing
When this bit is set, the 24-bit signed value in the start
address of the move is treated as a relative displacement
from the value in the
register. Both the transfer count and the source/
destination address are fetched from this location.
Use the signed integer offset in bits [23:0] of the second
four bytes of the instruction, added to the value in the
register, to fetch first the
byte count and then the data address. The signed value
is combined with the data structure base address to
generate the physical address used to fetch values from
the data structure. Sign extended values of all ones for
negative values are allowed, but bits [31:24] are ignored.
Note:
Do not use indirect and table indirect addressing
simultaneously; use only one addressing method at a time.
Prior to the start of an I/O, the
register should be loaded with the base address of
the I/O data structure. The address may be any address
on a longword boundary.
Command
Not Used
Don’t Care
Table Offset