sii3114 Silicon image, sii3114 Datasheet - Page 90

• Manufacturer Part Number: sii3114
• Description: Pci To Serial Ata Controller
• Manufacturer: Silicon image

SiI3114 PCI to Serial ATA Controller
Data Sheet
Second PCI Bus Master Registers Usage
In order to provide backward compatibility with existing drivers, the Physical Region Descriptor (PRD) tables used
by the SiI3114 controller when performing DMA transfers suffer the following limitations; a PRD table entry cannot
represent a memory area greater than 64k, nor can a PRD table entry represent a memory area that spans a 64k
address boundary. Whenever DMA is initiated via the PCI Bus Master – Channel x registers, the foregoing
limitations are enforced by the SiI3114 controller.
A feature known as Large Block Transfer in the SiI3114 controller allows drivers to get around the 64k size and
address limits of PRD table entries expected by existing drivers. Large Block Transfer simplifies the creation of
PRD tables by reducing the number of table entries that need to be created and eliminating the need to make
sure a memory region does not cross a 64k boundary. Large Block Transfer mode is enabled whenever DMA is
initiated by writing to the PCI Bus Master 2 – Channel x registers (base address 5, offset 10
When performing DMA in Large Block Transfer mode, the SiI3114 controller interprets the fields of a PRD table
entry differently. In all other respects, DMA interrupt generation, DMA status bit interpretation, etc., Large Block
Transfer mode behaves identically to a non-Large Block Transfer mode DMA operation. Table 27 describes the
format of a PRD table entry.
SiI-DS-0103-D
47:32
62:48
31:0
Bits
63
Function
32-bit starting address of the memory region.
When not operating in Large Block Transfer mode, this field specifies the size of the memory region. If the
size of the memory region is greater than 64k, or crosses a 64k address boundary, then two or more PRD
table entries will need to be created to describe it.
If operating in Large Block Transfer mode, this field contains the least significant 16-bits of the size of the
memory region.
If not operating in Large Block Transfer mode, this field is unused.
If operating in Large Block Transfer mode, this field contains the most significant 15-bits of the size of the
memory region.
When set, this bit indicates that this is the last entry in the PRD table.
Table 27. Physical Region Descriptor (PRD) Format
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© 2007 Silicon Image, Inc.
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Silicon Image, Inc.
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