operation is performed, one of the six selector registers below will be used to generate a 64-bit address.

If the selector for a particular device operation is zero, then a standard 32-bit address cycle will be generated. If the selector value is nonzero, then a DAC will be issued and the 64-bit address will be presented in two address phases.

All selectors default to 0 (zero) with the exception of the 16 SCRATCH registers, these power-up in an indeterminate state and should be initialized before they are used.

All selectors can be read/written using the Load and Store SCRIPTS instruction, Memory-to-Memory Move, Read/Write SCRIPTS instruction, or CPU with SCRIPTS not running.

Note: Crossing of selector boundaries in one memory operation is not supported.

Registers: 0xA0–0xA3

Memory Move Read Selector (MMRS)

Read/Write

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MMRS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MMRS

 

 

 

Memory Move Read Selector (MMRS)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Supplies the upper Dword of a 64-bit address during data

 

 

 

 

 

 

 

 

 

 

 

 

 

 

read operations for Memory-to-Memory Moves and

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

absolute address LOAD operations.

 

 

 

 

 

 

 

 

 

A special mode of this register can be enabled by setting the PCI Configuration Enable bit in the Chip Test Two (CTEST2) register. Because the LSI53C875A supports only a 32-bit memory mapped PCI base address, the MMRS register is always read as 0x00000000 when in the special mode.

Writes to the MMRS register are unaffected. Clearing the PCI Configuration Into Enable bit causes the MMRS register to return to normal operation.

4-100Registers

Page 192
Image 192
LSI 53C875A technical manual Registers 0xA0-0xA3, Memory Move Read Selector Mmrs Read/Write