DCV

Data Compare Value

[7:0]

 

 

This 8-bit field is the data compared against the register.

 

 

These bits are used in conjunction with the Data

 

 

 

Compare Mask Field to test for a particular data value.

5.6.2 Second Dword

 

 

 

 

31

 

 

 

 

0

 

 

 

 

 

 

 

 

DMA SCRIPTS Pointer Save (DSPS) Register

 

 

 

 

x x x x x x x x

x x x x x x x x

x x x x x x x x

x x x x x x x x

 

 

 

 

 

 

 

 

Jump Address

[31:0]

 

 

This 32-bit field contains the address of the next

 

instruction to fetch when a jump is taken. Once the LSI53C875A fetches the instruction from the address pointed to by these 32 bits, this address is incremented by 4, loaded into the DMA SCRIPTS Pointer (DSP) register and becomes the current instruction pointer.

5.7 Memory Move Instructions

For Memory Move instructions, bits 5 and 4 (SIOM and DIOM) in the DMA Mode (DMODE) register determine whether the source or destination addresses reside in memory or I/O space. By setting these bits appropriately, data may be moved within memory space, within I/O space, or between the two address spaces.

The Memory Move instruction is used to copy the specified number of bytes from the source address to the destination address.

Allowing the LSI53C875A to perform memory moves frees the system processor for other tasks and moves data at higher speeds than available from current DMA controllers. Up to 16 Mbytes may be transferred with one instruction. There are two restrictions:

Both the source and destination addresses must start with the same address alignment A[1:0]. If the source and destination are not aligned, then an illegal instruction interrupt occurs. For the PCI Cache Line Size register setting to take effect, the source and destination must be the same distance from a cache line boundary.

5-32

SCSI SCRIPTS Instruction Set

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LSI 53C875A technical manual Memory Move Instructions, Dcv, Data Compare Value, Jump Address 310