USB4/TBT3 Sideband (SB) Channel

USB4 can simultaneously transmit DisplayPort video and PCIE signals through Intel Tunneled technology, and also support PD (Power Delivery) fast charging technology.
USB4 is backward compatible with USB 2.0 and USB 3.2 Gen1/Gen2 and supports Thunderbolt 3/4. The sideband channel (SB) was originally defined as a channel for video protocol communication after entering the Alt-Mode (Alternate Mode) in USB 3.2 (for example: DP Alt-Mode transmits AUX signals through the Sideband channel...etc.). In the USB4 specification, new features of Sideband channel are added to confirm whether the USB4 interface is connected, start and close the channel, initialize the channel, and enter or leave the sleep mode. Thunderbolt Alt-Mode will be enabled when connecting to the device via Thunderbolt 3.

Application: The connection between the USB4/TBT3 Ports of two interconnected Routers that provides initial communication and setup functionality.
Functions: Link Parameter Negotiation, Lane Assignment, Gen Setting, Coding, Lane Equalization.
Signal: Sideband Transactions are sent over SBTX and received over the SBRX
Voltage: 3.3V

Logic Analyzer

TB3016F

TB3000 series Specifications PDF

MSO2116E (w/ analog channels)

MSO2000 series Specifications PDF

Waveform & Decode

Report

Protocol Quick Setup:

1. Click Quick Settings to select a protocol for logic analyzer capture.

2. Select USB4/TBT3 SB for decoding.

3. The system provides recommended settings for trigger type, sampling rate, voltage threshold, and channel settings.

4. Click the icon to access the Decode Settings screen.

Decode Settings:

Channel:
Sideband TX: Show the selected channel.
Sideband RX: It is checked by default, and the dual-channel analysis mode can be enabled by checking Sideband RX.
Data Convert: TX is checked by default, and the TX/RX channel can be selected for analysis in the data convert field.
Show on Report: TX and RX is checked by default. Choose which channel to display in the report area, and both channels can be displayed at the same time.

Others:
Version: USB4 2.0 is checked by default, and different versions can be selected for USB4/TBT3 SB signal analysis.
Show scale on data convert: The default is off. Show the scale on data convert field.
Show data detail on report: The default is off. If checked, additional data information will show on report as shown below.

YouTube Videos

USB4/TBT3 Sideband (SB) Channel Decoding Examples