Protocol analysis
R&S
®
RTP
830User Manual 1337.9952.02 ─ 12
Specific protocol features
Key features of USB 3.1 Gen 1 that are addressed by option R&S RTP-K61 include:
●
Since 5 Gbps is too fast for serial pattern triggering, the option uses a search-
based software trigger
●
The protocol uses a non-return-to-zero (NRZ) unclocked signal with 8b/10b encod-
ing (while USB 3.1 Gen 2 uses 128b/132b encoding)
●
The signal is scrambled with a 32-bit minimum correlation sequence
●
COMMA (K28.5), which occurs only during the reset phase, is the only unique bit
sequence
– COMMA is used for reset of the scrambling sequence, which has 32-bit mini-
mum correlation
– COMMA and packet framing are used for bit alignment
●
The protocol uses a set of different frame types that are all covered by individual
trigger and search dialogues of option R&S RTP-K61
Frame types
All frame types are listed below. The frame types are sorted in an almost alphabetical
order, as in the oscilloscope's graphical user interface (GUI).
Each item in this list contains:
●
the SCPI name of the frame
(hence the name of the frame according to the related remote control com
mand (SCPI))
●
the GUI name of the frame, which is sometimes identical with the SCPI name
(the GUI names are highlighted in bold font and linked to one of Table 13-32 /
Table 13-33 / Table 13-34)
●
a brief description of the frame type
List of frame types
●
ACK - ACK = Handshake packet indicating a positive acknowledgment.
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BCNT - BCNT = BERT count, with BERT = Bit Error Rate Test. BCNT is a K28.3
sequence followed by the error count symbol EC. See also BERC.
●
BDAT - BDAT = BERT data, ordered set of a BERT command. This data sequence
(output of the scrambler) is used for BER testing and is equivalent to the logical
idle sequence, consisting of scrambled 0.
●
BERC - BERC = BERT error count, ordered set of a BERT command that does not
increment the error count register. BERC is not looped back to the receiver but
replaced with BCNT.
●
BRST - BRST = BERT reset, ordered set of a BERT command. Any time a BRST
is received, the error count register EC is set to 0 and the linear feedback shift reg-
ister (LFSR) for scrambling is set to 0FFFFh. Any number of consecutive BRST
ordered sets may be received.
●
BIAM - Bus Interval Adjustment = The bus interval is the period that establishes
the integral boundary of service intervals. It is equivalent to the Microframe interval
(THSFRAM) defined in the USB 2.0 specification.
USB 3.1 (option R&S
RTP-K61/K62)
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