Registers: 0x28–0x2B

DMA Next Address (DNAD)

Read/Write

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DNAD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

 

0

0

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DNAD

 

 

 

DMA Next Address

 

 

 

 

 

 

 

 

 

 

[31:0]

This 32-bit register contains the general purpose address pointer. At the start of some SCRIPTS operations, its value is copied from the DMA SCRIPTS Pointer Save (DSPS) register. Its value may not be valid except in certain abort conditions. The default value of this register is zero.

Registers: 0x2C–0x2F

DMA SCRIPTS Pointer (DSP)

Read/Write

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DSP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DSP

 

 

 

DMA SCRIPTS Pointer

 

 

 

 

 

 

 

 

 

[31:0]

To execute SCSI SCRIPTS, the address of the first SCRIPTS instruction must be written to this register. In normal SCRIPTS operation, once the starting address of the SCRIPT is written to this register, SCRIPTS are automatically fetched and executed until an interrupt condition occurs.

In single step mode, there is a single step interrupt after each instruction is executed. The DMA SCRIPTS Pointer (DSP) register does not need to be written with the next address, but the Start DMA bit (bit 2, DMA Control (DCNTL) register) must be set each time the step interrupt occurs to fetch and execute the next SCRIPTS command. When writing this register eight bits at a time, writing the upper eight bits begins execution of SCSI SCRIPTS. The default value of this register is zero.

See Section 5.4.2, “Second Dword,”for register detail.

4-64Registers

Page 156
Image 156
LSI 53C875A technical manual Registers 0x2C-0x2F, Dnad, Dsp