USB3.2超高速协议规范
USB3.2超高速GEN1、GEN2特殊符号（symbol）和链路管理
2021-06-06
2756
1
8b/10b编码方案提供与数据不同的特殊符号（symbol）用来表示字符的符号。这些特殊符号用于各种链接管理机制。
特殊符号应遵循适当的8b/10b差异规则。
对于GEN2，块头标识如果以下16个符号代表数据，则它们具有特殊含义。在GEN2中，当是控制块的一部分,接收机在接收特殊符号时，应始终对其进行单比特纠错。对于1代和2代，定义了以下特殊符号。
| Symbol | Name | “Gen 1 Symbol” | “Gen 2 Symbol” | Description |
|---|---|---|---|---|
| SKP | Skip | K28.1 | CCh | “Compensates for different bit rates between two communicating ports. SKPs may be dynamically inserted or removed from the data stream. For Gen 2 operation, unscrambled.” |
| SKPEND | Skip End | “Not applicable” | 33h | “Marks the boundary between SKP symbols and the remainder of the SKP OS. Unscrambled.” |
| SDP | “Start Data Packet” | K28.2 | 96h | “Marks the start of a Data Packet Payload. For Gen 2 operation, scrambled and transmitted only in data block.” |
| EDB | End Bad | K28.3 | 69h | “Marks the end of a nullified Packet. For Gen 2 operation, scrambled and transmitted only in data block.” |
| SUB | “Decode Error Substitution” | K28.4 | “Not applicable” | “Symbol substituted by the 8b/10b decoder when a Decode error is detected.” |
| COM | Comma | K28.5 | “Not applicable” | Used for symbol alignment. |
| ——- | ——- | K28.6 | “Not applicable” | Reserved |
| SHP | “Start Header Packet” | K27.7 | 9Ah | “Marks the start of a Data Packet (Gen 1 operation only), Transaction Packet or Link Management Packet. For Gen 2 operation, scrambled and transmitted only in data block.” |
| DPHP | “Start Data Packet Header” | “Not applicable” | 95h | “Marks the start of a Data Packet (Gen 2 only).Scrambled and transmitted only in data block.” |
| END | End | K29.7 | 65h | “Marks the end of a packet. For Gen 2 operation, scrambled and transmitted only in data block.” |
| SLC | “Start Link Command” | K30.7 | 4Bh | “Marks the start of a Link Command. For Gen 2 operation, scrambled and transmitted only in data block.” |
| EPF | “End Packet Framing” | K23.7 | 36h | “Marks the end of a packet framing. For Gen 2 operation, scrambled and transmitted only in datablock.” |
| SDS | “Start of Data Stream” | “Not applicable” | E1h | “Marks the start of an SDS Ordered Set.Unscrambled.” |
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