最近在看PCIE 資料，整理了一些筆記
以下是TLP header 字段的總結
| header filed | header location | filed Use | 備註 |
| Fmt[1:0] | bits 6:5 of byte 0 | 00b ：3 DW header, no data 01b ：4 DW header, no data 10b ：3 DW header, with data 11b ：4 DW header, with data |
common |
| Type[4:0] | bits 4:0 of byte 0 | 0 0000 ：MRd ，Fmt[1:0] 00 or 01，Memory Read Request 0 0001 ：MRdLk ，Fmt[1:0] 00 or 01，Memory Read Request-Locked 0 0000 ：MWr ，Fmt[1:0] 10 or 11，Memory Write Request 0 0010 ：IORd ，Fmt[1:0] 00，I/O Read Request 0 0010 ：IOWr，Fmt[1:0] 10，I/O Write Request 0 0100 ：CfgRd0，Fmt[1:0] 00，Configuration Read Type 0 0 0100 ：CfgWr0，Fmt[1:0] 10，Configuration Write Type 0 0 0101 ：CfgRd1，Fmt[1:0] 00，Configuration Read Type 1 0 0101 ：CfgWr1，Fmt[1:0] 10，Configuration Write Type 1 1 0r2r1r0：Msg，Fmt[1:0] 01，Message Request，r2r1r0 specifies the Message routing mechanism 1 0r2r1r0：MsgD，Fmt[1:0] 11，Message Request with data payload 0 1010 ：Cpl，Fmt[1:0] 00，Completion without Data– Used for I/O and Configuration Write Completions and Read Completions (I/O, Configuration, or Memory) with Completion Status other than Successful Completion. 0 1010 ：CplD，Fmt[1:0] 10，Completion with Data – Used for Memory, I/O, and Configuration Read Completions 0 1011 ：CplLk，Fmt[1:0] 00，Completion for Locked Memory Read without Data – Used only in error case 0 1011 ：CplDLk，Fmt[1:0] 10，Completion for Locked Memory Read –otherwise like CplD. |
common |
| TC[2:0] | bits [6:4] of byte 1 | Traffic Class, differentiation of transactions into eight traffic classes |
common |
| Attr[1:0] | bits [5:4] of byte 2 | bit 5: relaxed ordering，允許某些事務（TRANSACTION）提前執行，而不是按先前的執行順序，從而提高系統性能 0：Default Ordering，PCI Strongly Ordered Model 1：Relaxed Ordering，PCI-X Relaxed Ordering Model bit 4 ：No Snoop 0：Default，Hardware enforced cache coherency expected 1：No Snoop，Hardware enforced cache coherency not expected |
common |
| TD | bit 7 of byte 2 | 1b indicates presence of TLP digest in the form of a single DW at the end of the TLP | common |
| EP | bit 6 of byte 2 | Error Forwarding：indicates the TLP is poisoned optional |
common （Write Request (Posted or Non-Posted) or a Read Completion） |
| Length[9:0] | bits 1:0 of byte 2 bits 7:0 of byte 3 | Length of data payload in DW 00 0000 0001b：1 DW 00 0000 0010b：2 DW … ：... 11 1111 1111b：1023 DW 00 0000 0000b：1024 DW |
common |
| Address[63:0] | 64bits address : all bits of byte8-15 32bits address : bits of byte8-11 |
address routing | |
| bus Number[7:0] | Bits 7:0 of Byte 8 | specify the destination Device for the TLP | ID routing |
| Device Number[4:0] | Bits 7:3 of Byte 9 | ||
| Function Number[2:0] | Bits 2:0 of Byte 9 | ||
| Request ID[15:0] | all bits of byte 4-5 | [15:8]:bus Number[7:0] [7:3] :Device Number [2:0]:Function Number |
Transaction ID is included with all Requests and Completions |
| tag[7:0] | bits [7:0] of byte 6? | 由產生請求包的器件生成的，如果請求器件需要應答，則每個Tag[7:0]是獨一無二的 1.By default, only the lower 5 bits of the Tag field are used with the remaining upper 3 bits required to be all 0’s 2.If the Extended Tag Field Enable（Device Control Register ） bit is set,the maximum is increased to 256(default 32), and the entire Tag field is used 3.For Requests which do not require Completion (Posted Requests), the value in the Tag[7:0] field is undefined and may contain any value |
Request ID+Tag = Transaction ID |
| first DW BE[3:0] | bits[3:0] of Byte7 | [0]: affected data Byte 0 [1]: affected data Byte 1 [2]: affected data Byte 2 [3]: affected data Byte 3 |
Memory, I/O, and Configuration Requests |
| Last DW BE[3:0] | bits[7:4] of Byte7 | [0]: affected data Byte N-4 [1]: affected data Byte N-3 [2]: affected data Byte N-2 [3]: affected data Byte N-1 Assuming the data referenced is N bytes in length (Byte 0 to Byte N-1) |
|
| Completer ID[15:0] | all bits of byte 4-5 | Identifies the Completer [15:8]:bus Number[7:0] [7:3] :Device Number [2:0]:Function Number |
Completion |
| Completion Status[2:0] | bit 7:5 of byte6 | Indicates the status for a Completion 000b: Successful Completion (SC),請求（Request）被正確的處理 001b: Unsupported Request (UR),表示請求是非法的或者不能被Completer所識別的 010b: Configuration Request Retry Status (CRS),Completer暫時不能響應的配置請求，需要Requester稍後再次嘗試 100b: Completer Abort (CA),Completer可以響應該請求，但是卻發生了其他的錯誤，該錯誤是Uncorrectable Error all others: Reserved |
Completion |
| BCM | Byte Count Modified must not set by PCI Express Completers, and may only be set by PCI-X completers |
Completion | |
| Byte Count[11:0] | bit 3:0 of byte6 bit 7:0 of byte7 |
The remaining byte count for Request 0000 0000 0000b : 4096 bytes 0000 0000 0001b : 1 byte …… 1111 1111 1111b : 4095 bytes |
Completion |
| tag[7:0] | bit 7:0 of byte10 | in combination with the Requester ID field, corresponds to the Transaction ID | Completion |
| Lower Address[6:0] | bit 6:0 of byte11 | lower byte address for starting byte of Completion | Completion |
| 僅針對pcie 1.0a，不同的版本會有所不同 | |||