Snoop Cycle Overlaying A Non-Burst Cycle - Intel Quark SoC X1000 Core Developer's Manual

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Bus Operation—Intel Quark Core
10.4.3.2.2 AHOLD Snoop Overlaying a Non-Burst Cycle
When AHOLD overlays a non-burst cycle, snooping is based on the completion of the
current non-burst transfer (ADS#-RDY# transfer).
under AHOLD overlaying a non-burst line-fill cycle. HITM# is asserted two clocks after
EADS#, and the non-burst cycle is fractured after the RDY# for a specific single
transfer is asserted. The snoop write-back cycle is re-ordered ahead of an ongoing non-
burst cycle. After the write-back cycle is completed, the fractured non-burst cycle
continues. The snoop write-back ALWAYS precedes the completion of a fractured cycle,
regardless of the point at which AHOLD is de-asserted, and AHOLD must be de-
asserted before the fractured non-burst cycle can complete.
Figure 115. Snoop Cycle Overlaying a Non-Burst Cycle
CLK
AHOLD
EADS#
INV
HITM#
ADS#
A31–A4
A3–A2
RDY#
CACHE#
BLAST#
W/R#
10.4.3.2.3 AHOLD Snoop to the Same Line that is being Filled
A system snoop does not cause a write-back cycle to occur if the snoop hits a line while
the line is being filled. The processor does not allow a line to be modified until the fill is
completed (and a snoop only produces a write-back cycle for a modified line). Although
a snoop to a line that is being filled does not produce a write-back cycle, the snoop still
has an effect based on the following rules:
1. The processor always snoops the line being filled.
2. In all cases, the processor uses the operand that triggered the line fill.
October 2013
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1 2 3 4 5 6 7
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Fill
0
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To Processor
‡
Write-back from Processor
Figure 115
8 9 10 11 12 13 14 15
‡
0 4 8 C
shows a snoop cycle
16 17 18 19 20 21 22 23
Fill Cont.
4 8 C
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Intel Quark SoC X1000 Core
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