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5-34 SCSI SCRIPTS Instruction Set
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 LSI53C875A responds to addresses as defined in the Base
Address Register Zero (I/O) or Base Address Register 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 SFBR is not writable using the CPU, and therefore not by a Memory
Move. However, it can be loaded using SCRIPTS Read/Write operations.
ToloadtheSFBRwithabytestoredinsystemmemory,firstmovethe
byte to an intermediate LSI53C875A register (for example, a SCRATCH
register), and then to the 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.
31 0
DMA SCRIPTS Pointer Save (DSPS) Register
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