PCI Functional Description
2-9
2.1.2.13 Memory Write and Invalidate Command
The Memory Write and Invalidate command is identical to the Memory
Write command, except it additionally guarantees a minimum transfer of
one complete cache line. That is, the master intends to write all bytes
within the addressed cache line in a single PCI transaction unless
interrupted by the target. This command requires implementation of the
PCI
register. The LSI53C1000 enables Memory
Write and Invalidate cycles when bit 0 (WRIE), in the
register, and bit 4 (WIE), in the PCI
register, are
set.
When the following conditions are met, Memory Write and Invalidate
commands are issued:
•
The following bits are set:
–
The CLSE bit (Cache Line Size Enable, bit 7, of the
register),
–
The WRIE bit (Write and Invalidate Enable, bit 0, of the
register),
–
Bit 4 of the PCI Configuration
register.
•
The
register contains a legal burst size value
(8, 16, 32, 64, or 128 Dwords) that is less than or equal to the
burst size.
•
The chip has enough bytes in the DMA FIFO to complete at least
one full cache line burst.
•
The chip is aligned to a cache line boundary.
When these conditions are met, the LSI53C1000 issues a Write and
Invalidate command instead of a Memory Write command during all PCI
write cycles.
Multiple Cache Line Transfers – The Memory Write and Invalidate
command can write multiple cache lines of data in a single bus
ownership. The chip issues a burst transfer as soon as it reaches a
cache line boundary. The transfer size is not automatically the cache line
size, but rather a multiple of the cache line size specified in Revision 2.2
of the PCI specification. The logic selects the largest multiple of the
cache line size based on the transfer size. The maximum allowable burst
size is determined from the
burst size bits, and
Содержание LSI53C1000
Страница 6: ...vi Preface...
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Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
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Страница 360: ...A 8 Register Summary...
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