L-tile and H-tile Avalon® Memory-mapped Intel® FPGA IP for PCI Express* User Guide

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ID 683667
Date 11/11/2021
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4.4.3. MSI and MSI-X Capabilities

Table 20.  MSI and MSI-X Capabilities 

Parameter

Value

Address

Description

MSI messages requested

1, 2, 4, 8, 16, 32

0x050[31:16]

Specifies the number of messages the Application Layer can request. Sets the value of the Multiple Message Capable field of the Message Control register.

MSI-X Capabilities

Implement MSI-X

On/Off

 

When On, adds the MSI-X capability structure, with the parameters shown below.

Bit Range  

Table size

[10:0]

0x068[26:16]

System software reads this field to determine the MSI-X Table size <n>, which is encoded as <n–1>. For example, a returned value of 2047 indicates a table size of 2048. This field is read-only in the MSI-X Capability Structure. Legal range is 0–2047 (211).

Table offset

[31:0]

 

Points to the base of the MSI-X Table. The lower 3 bits of the table BAR indicator (BIR) are set to zero by software to form a 64-bit qword-aligned offset. This field is read-only.

Table BAR indicator

[2:0]

 

Specifies which one of a function’s BARs, located beginning at 0x10 in Configuration Space, is used to map the MSI-X table into memory space. This field is read-only. Legal range is 0–5.

Pending bit array (PBA) offset

[31:0]

 

Used as an offset from the address contained in one of the function’s Base Address registers to point to the base of the MSI-X PBA. The lower 3 bits of the PBA BIR are set to zero by software to form a 32-bit qword-aligned offset. This field is read-only in the MSI-X Capability Structure. 5

Pending BAR indicator

[2:0]

 

Specifies the function Base Address registers, located beginning at 0x10 in Configuration Space, that maps the MSI-X PBA into memory space. This field is read-only in the MSI-X Capability Structure. Legal range is 0–5.

5 Throughout this user guide, the terms word, DWORD and qword have the same meaning that they have in the PCI Express Base Specification. A word is 16 bits, a DWORD is 32 bits, and a qword is 64 bits.

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