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Table 50: Requester Request Descriptor Fields (cont'd)
Bit Index
Field Name
Description
87:80
Requester Function/ Device
Number
Device and/or Function number of the Requester Function.
Endpoint mode:
•
ARI enabled:
○
Bits [87:80] must be set to the Requester Function number.
•
ARI disabled:
○
Bits [82:80] must be set to the Requester Function number.
○
Bits [87:83] are not used
Upstream Port for Switch use case (Endpoint mode is selected within
the IP):
•
ARI enabled:
○
Bits [87:80] must be set to the Requester Function number.
•
ARI disabled:
○
Bits [82:80] must be set to the Requester Function number.
○
Bits [87:83] are not used if the request is originating from the
switch itself. These bits must be set to the Requester Device
number where the request was originated if the switch is
relaying the request (Requester is external to the switch).
This is used in conjunction with Requester ID Enable bit in the
descriptor.
Root Port mode (Downstream Port):
•
ARI enabled:
○
Bits [87:80] must be set to the Requester Function number.
•
ARI disabled:
○
Bits [87:80] must be set to the Requester Function number.
○
Bits [87:83] must be set to the Requester Device number. This
is used in conjunction with Requester ID Enable bit in the
descriptor.
95:88
Requester Bus Number
Bus number associated with the Requester Function.
Endpoint mode:
•
Not used
Upstream Port for Switch use case (Endpoint mode is selected within
the IP):
•
Not used if the request is originating from the switch itself. These
bits must be set to the Requester Bus number where the request
was originated if the switch is relaying the request (Requester is
external to the switch). This is used in conjunction with Requester
ID Enable bit in the descriptor.
Root Port mode (Downstream Port):
•
Must be set to the Requester Bus number. This is used in
conjunction with Requester ID Enable bit in the descriptor.
103:96
Tag
PCIe Tag associated with the request. For Posted transactions, the
core always uses the value from this field as the tag for the request.
For Non-Posted transactions, the core uses the value from this field if
the Enable Client Tag is set during core configuration in the Vivado
IDE (that is, when tag management is performed by the user logic). If
this attribute is not set, tag management logic in the core is
responsible for generating the tag to be used, and the value in the
tag field of the descriptor is not used.
Chapter 4: Designing with the Core
PG346 (v3.3) November 16, 2022
CPM Mode for PCI Express
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