PCIe Capabilities List

PCIe Configuration space

PCIe take PCI Of 256Bytes The configuration space is extended to 4096bytes.PCIe The configuration space can be divided into two parts ：256bytes Of PCI Compatible with some configuration spaces and PCIe Expand the configuration space .

and PCIe Of Capabilities List It's also divided into two parts ：PCI Compatible parts and PCIe Extension part Capabilities List.

PCI Capabilities List

stay PCI2.1 Add some abilities after , The protocol is added according to the linked list , This management Capabilities The linked list is called Capabilities;

Whether or not this linked list exists can be saved through PCI Status Register Of bit4（Capabilities List） instructions , When it is 1 Indicates presence ; Otherwise, it does not exist ;0x34h Indicates the first Capabilities The pointer to ;

In each table Capability Include 8bit ID Domain ,ID from PCI SIG Distribute ;8bit The pointer to , Points to the next... In the table Capabilities The location of （ When its value is 0x00h It means the end of the linked list ）; And some other registers to perform correlation Capabilities, These registers are followed by the previous registers ;

The above example constructs a simple Capabilities List.0x34h Point to the first one Capabilities The location of , Yes 0xA4h, There is a ID, next Capabilities The pointer points to 0x5Ch, And contains other related registers ;

0xA4h Yes 0x5Ch;0x5Ch Point to 0xE0h;0xE0h Point to 0x0 Indicates that the linked list is over .

PCIe Extended Capabilities List

PCIe Extended Capabilities List and PCI Different ; The relevant registers are placed in 0x100 And higher address locations ; first PCIe Extended Capabilities Register fixed in 0x100 Location , Include 16bit Of Capabilities ID、4bit Capabilities Version Number and 12bit Next Capabilities Offset; Other forms are similar to the above ;