Avago Technologies LSI53C876E User Manual
Page 197
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 specification of a table of data
buffer addresses. Using the SCSI SCRIPTS compiler, 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.
Note:
Do not use indirect and table indirect addressing
simultaneously; use only one addressing method at a time.
TIA
Table Indirect
28
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.
illustrates the Block Move Instruction register.
Command
Not Used
Don’t Care
Table Offset