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Table 37: Configuration Flow Control Interface (cont'd)
Port
I/O
Width
Description
pcie0_cfg_fc_cplh_scale
O
2
Completion Header Flow Control Credit Scale
This output provides the scale of Completion Header Flow
Control Credit number (cfg_fc_cplh). The flow control
information to bring out on this core is selected by the
cfg_fc_sel[2:0] input.
pcie0_cfg_fc_cpld
O
12
Completion Data Flow Control Credits.
This output provides the number of Completion Data
Flow Control Credits. This multiplexed output can be used
to bring out various flow control parameters and
variables related to Completion Data Credit maintained
by the core. The flow control information to bring out on
this core is selected by the cfg_fc_sel[2:0].
pcie0_cfg_fc_cpld_scale
O
2
Completion Data Flow Control Credit Scale
This output provides the scale of Completion Data Flow
Control Credit number (cfg_fc_cpld). The flow control
information to bring out on this core is selected by the
cfg_fc_sel[2:0] input.
pcie0_cfg_fc_vc_sel
pcie1_cfg_fc_vc_sel
I
1
Flow Control Informational Virtual Channel Select: Selects
the Virtual Channel for the type of flow control
information presented on the trn_fc_* signals. Possible
values:
0b = VC0
1b = VC1
pcie0_cfg_fc_sel
pcie1_cfg_fc_sel
I
3
Flow Control Informational Select.
These inputs select the type of flow control to bring out
on the cfg_fc_* outputs of the core. The various flow
control parameters and variables that can be accessed for
the different settings of these inputs are:
•
000: Receive credit limit to link partner (rlimit)
•
001: Transmit credits consumed (tconsumed) & wide
posted and completion
•
010: Receive credits consumed by link partner
(rconsumed)
•
011: Transmit credits consumed (tconsumed) wide
nonposted and completion
•
100: Transmit user credits available (tlimit -
tconsumed)
•
101: Transmit credit limit (tlimit)
•
110: Transmit credits consumed (tconsumed)
•
111: Receive free 32B word count
This value represents the actual unused credits in the
receiver FIFO, and the recommendation is to use it only as
an approximate indication of receiver FIFO fullness,
relative to the initial credit limit value advertized, such as,
¼ full, ½ full, ¾ full, full.
Infinite credit for transmit credits available (cfg_fc_sel ==
3'b100) is signaled as 8'h80, 12'h800 for header and data
credits, respectively. For all other cfg_fc_sel selections,
infinite credit is signaled as 8'h00, 12'h000, respectively,
for header and data categories.
Chapter 3: Product Specification
PG346 (v3.3) November 16, 2022
CPM Mode for PCI Express
107