Avago Technologies LSI53C825AE - Manual (Page 222)

5-38 SCSI SCRIPTS Instruction Set
TC[23:0] Transfer Counter [23:0]
The number of bytes to transfer is stored in the lower
24 bits of the first instruction word.
5.7.2 Read/Write System Memory from SCRIPTS
By using the Memory Move instruction, single or multiple register values
are transferred to or from system memory.
Because the LSI53C825A responds to addresses as defined in the Base
Address Zero (I/O) or Base Address One (Memory) registers, it can be
accessed during a Memory Move operation if the source or destination
address decodes to within the chip’s register space. If this occurs, the
register indicated by the lower seven bits of the address is taken as the
data source or destination. In this way, register values are saved to
system memory and later restored, and SCRIPTS can make decisions
based on data values in system memory.
The SCSI First Byte Received (SFBR) is not writable using the CPU, and
therefore not by a Memory Move. However, it can be loaded using
SCRIPTS Read/Write operations. To load the SFBR with a byte stored
in system memory, first move the byte to an intermediate LSI53C825A
register (for example, a SCRATCH register), and then to the
SCSI First
Byte Received (SFBR) .
The same address alignment restrictions apply to register access
operations as to normal memory-to-memory transfers.
5.7.3 Second Dword
DSPS Register [31:0]
These bits contain the source address of the Memory
Move.
5.7.4 Third Dword
TEMP Register [31:0]
These bits contain the destination address for the
Memory Move.
Figure 5.6 illustrates the Memory Move instruction.