USB Type-C™ / USB Power Delivery interface (UCPD) RM0440
2046/2126 RM0440 Rev 4
46.4.3 Physical layer protocol
The physical layer covers the signaling underlying the USB Power Delivery specification.
On the transmitter side its main function is to form packets according to the defined packet
format including generally:
• preamble
• start of packet (SOP, ordered set)
• payload header
• payload data
• cyclic redundancy check (CRC) information
• end of packet (EOP)
Before going on the CC line, the data stream is BMC-encoded, respecting specified timing
restrictions.
On the receive side, the principle task is to:
• extract start of packet (SOP, ordered set) information
• extract payload header
• extract payload data
• receive and check CRC
• receive end of packet (EOP)
The receive is basically a reverse of the transmit process, thus starting with BMC data
stream decoding.
Symbol encoding
Apart from the preamble all symbols are encoded with a 4b5b scheme according to the
specification shown in the following table.
Table 421. 4b5b Symbol Encoding Table
Name 4b 5b Symbol description
0 0000 11110 hex data 0
1 0001 01001 hex data 1
2 0010 10100 hex data 2
3 0011 10101 hex data 3
4 0100 01010 hex data 4
5 0101 01011 hex data 5
6 0110 01110 hex data 6
7 0111 01111 hex data 7
8 1000 10010 hex data 8
9 1001 10011 hex data 9
A 1010 10110 hex data A
B 1011 10111 hex data B
C 1100 11010 hex data C
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