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7–44 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
PCI Master Operation
Table 7–15 specifies the ordering rules and behavior for the
PCI-to-Avalon direction. The entries in this table describe whether a type
in a row may pass a type in a column. The table uses the following
terminology: "No" means a type may not pass another type, "Yes/No"
means a type may pass the other type, but does not have to, and "Yes"
means that a type must pass another type to avoid deadlocks.
Table 7–15. Summary of Ordering in the PCI-to-Avalon Direction
PMW DRR DWR DRC DWC
Spec(1) Impl(2) Spec Impl Spec Impl Spec Impl Spec Impl
PMW No
No(3)
Ye s
No(5)
Ye s
N/A
Ye s
Ye s (6)
Ye s Ye s
DRR No No(3) Yes/ No No(5) Ye s / N o
N/A
Yes / No
Ye s (6)
Yes / No Ye s
DWR No No(3) Yes / N o
No(5)
Yes/ No
No(5)
Yes / No
Ye s (6)
Yes / No N o
DRC No
No(4)
Ye s
No(5)
Ye s
N/A
Yes / No
No(7)
Yes / No N o
DWC Yes/ No
No(4)
Ye s
No(5)
Yes No Yes/ No No Yes/ No No
Notes to Table 7–15:
(1) Spec refers to the PCI Local Bus Specification, Revision 3.0, published by PCI-SIG.
(2) Impl refers to the implementation of this passing rule in the PCI-Avalon bridge.
(3) PMWs and DRRs cannot pass other PMWs in the PCI-to-Avalon Command/Write Data buffer. Ordering logic will
prevent PMWs that hit prefetchable BARs and PMWs that hit non-prefetchable BARs from passing each other.
(4) The ordering logic prevents DRCs from passing PMWs
(5) Avalon-MM does not provide any mechanism to stop accepting reads separately from writes, so there is no way
to make PMWs, DRCs (or other DRRs) pass DRRs. However, since Avalon-MM provides completely separate
paths for master and slave transactions, the PCI requirements for this passing do not apply.
(6) PMWs and DRRs in the PCI-to-Avalon Buffers are allowed to pass DRCs in the Read Response buffers.
(7) Avalon-MM requires the DRCs (Read Responses) be returned in the order the requests were made. Note, however,
that DRCs may actually be returned in a different order than they completed on the PCI bus.
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