5.3.2 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

Start Address

[31:0]

This 32-bit field specifies the starting address of the data to move to/from memory. This field is copied to the DMA Next Address (DNAD) register. When the LSI53C875A transfers data to or from memory, the DNAD register is incremented by the number of bytes transferred.

When bit 29 is set, indicating indirect addressing, this address is a pointer to an address in memory that points to the data location. When bit 28 is set, indicating table indirect addressing, the value in this field is an offset into a table pointed to by the Data Structure Address (DSA). The table entry contains byte count and address information.

5.4 I/O Instruction

I/O Instructions perform the following SCSI operations in Target and Initiator mode. These I/O operations are chosen with the opcode bits in the DMA Command (DCMD) register.

OPC2

OPC1

OPC0

Target Mode

Initiator Mode

 

 

 

 

 

0

0

0

Reselect

Select

0

0

1

Disconnect

Wait Disconnect

0

1

0

Wait Select

Wait Reselect

0

1

1

Set

Set

1

0

0

Clear

Clear

 

 

 

 

 

This section describes these I/O operations.

I/O Instruction

5-13

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LSI 53C875A technical manual I/O Instruction, Second Dword, Start Address 310, Target Mode Initiator Mode