Altera Arria V Hard IP for PCI Express - Manual (Page 56)

4–4 Chapter 4: Parameter Settings for the Arria V Hard IP for PCI Express
Port Functions
Arria V Hard IP for PCI Express December 2013 Altera Corporation
User Guide
Device
Table 4–2 describes the shared device parameters.
Table 4–2. Capabilities Registers for Function (Part 1 of 2)
Parameter
Possible
Values
Default
Value
Description
Device Capabilities
Maximum
payload size
128
bytes
256
bytes,
512
bytes,
128 bytes
Specifies the maximum payload size supported. This
parameter sets the read-only value of the max payload size
supported field of the Device Capabilities register (
0x084 ) and
optimizes the IP core for this size payload. You should
optimize this setting based on your typical expected
transaction sizes.
Number of tags
supported
supported per
function
32
64
32
Indicates the number of tags supported for non-posted
requests transmitted by the Application Layer. This parameter
sets the values in the Device Capabilities register (0x084) of
the PCI Express Capability Structure described in
Table 8–8
on page 8–4 .
The Transaction Layer tracks all outstanding completions for
non-posted requests made by the Application Layer. This
parameter configures the Transaction Layer for the maximum
number to track. The Application Layer must set the tag
values in all non-posted PCI Express headers to be less than
this value. The Application Layer can only use tag numbers
greater than 31 if configuration software sets the
Extended
Tag Field Enable bit of the Device Control register.
This bit is available to the Application Layer as
cfg_devcsr[8] .
Completion
timeout range
ABCD
BCD
ABC
AB
B
A
None
ABCD
Indicates device function support for the optional completion
timeout programmability mechanism. This mechanism allows
system software to modify the completion timeout value. This
field is applicable only to Root Ports and Endpoints that issue
requests on their own behalf. This parameter sets the values
in the
Device Capabilities 2 register (0xA4) of the PCI
Express Capability Structure Version 2.1 described in
Table 8–8 on page 8–4 . For all other functions, the value is
None. Four time value ranges are defined:
■ Range A: 50 µs to 10 ms
■ Range B: 10 ms to 250 ms
■ Range C: 250 ms to 4 s
■ Range D: 4 s to 64 s
Bits are set to show timeout value ranges supported. 0x0000b
completion timeout programming is not supported and the
function must implement a timeout value in the range 50 s to
50 ms.