USB4 Recording Options

The Spread Spectrum Clock, Skew Measurements, and Link Detection Overrides recording options for the M4120, M480x, and M4x in USB4 Analyzer Mode appear in the USB4 > General pane (below). From the USB4 tab, you can also access various Triggers and Filters.

General Pane

Receiver Spread Spectrum Clock

This recording option automatically adjusts the “Receiver” logic on the analyzer ports to improve lock performance. Clear the checkboxes to disable.

Capture Skew Measurements

Enables capture of lane-to-lane skew measurements. These measurements are performed periodically on TSNOS packets, which must be present in the trace to obtain readings.

The accuracy is approximately +/- 5 ns.

Reset Link when Recording Options are applied

The analyzer cannot recover USB4 traffic if capture settings change while a link is active. When this option is enabled, the analyzer will momentarily break the link between analyzer ports whenever Recording Options are applied. This ensures the Host and Device establish a new link that can be captured.

Link Detection Overrides

Click Link Detection Overrides... to open the USB4 Link Detection Overrides dialog box. When any link detection setting is changed from its default value, the button is highlighted and displays a tooltip.

USB4 Link Detection Overrides Dialog Box

Click Restore Defaults to reset all override options in the dialog to their default values.

Protocol

• TBT3: Causes the software to interpret the packets and behavior according to the TBT3 specification. For example, if a new field is used in USB4 that was Reserved in TBT3, it will be shown as an error.

• USB4: Interprets all packets and behavior according to the USB4 specification.

Speed Mode

• Rounded: USB4 clock rate of 20.000 Gbps (Gen 3) or 10.000 Gbps (Gen 2)

• Legacy: TBT3 clock rate of 20.625 Gbps (Gen 3) or 10.3125 Gbps (Gen 2)

Speed

• Auto

• Gen 2

• Gen 3

• Gen 4 (M480x and M4120 only)

Link Width

• Auto

• Single-Link x1

• Symmetric x2

Lane Reversal

• No

• Yes

RS-FEC

• Auto

• FEC Encoded

• Non-FEC Mode

Pre-Coding

• Auto

• Enabled

• Disabled

Disable FEC Correction

Controls whether the Analyzer tries to apply FEC correction to its capture data, or ignores it. Default is to apply the corrections (checkboxes cleared)

• Lane 0

• Lane 1

Polarity Inversion

Same for All Links: Used to force a polarity regardless of that indicated in the training.

• Lane 0 Left – Auto Off/On

• Lane 0 Right – Auto Off/On

• Lane 1 Left – Auto Off/On

• Lane 1 Right – Auto Off/On

Triggers Pane

Simple Triggers Pane

Select Simple Triggers to open this pane. There are trigger options for Gen2/3 and Gen4, and Left or Right ports. Select any number of the items listed to cause a trigger to occur when the event is seen by the analyzer.

TLP Pattern Trigger

These are packets on the High Speed USB4 lanes. The first word denotes the USB4 Header which is one DWORD, followed by 4 DWORDS of untyped traffic.

Edit TLP Mask Match Pattern Options

When you select the Edit button in the Pattern Trigger, it launches a dialog box for editing the TLP.

You can select the Packet Category you want to trigger from the drop-down list. Categories include:

• Default

• Control Packet

• Link Mgmt Packet

• Time Sync Packet

• Tunneled PCIe Packet

• Tunneled USB3 Packet

• Tunneled DP Packet

• Tunneled DP AUX Packet

If you chose Tunneled PCIe Packet, the following options are available in DW0:

• PDF

• Supplemental ID

• HopID

• Length

• HEC

For PDF, you can choose from the following options:

• Ordered Set

• Electrical Idle State

• TLP/DLLP

• PERST Active

• PERST Inactive

An example with each option selected is shown in below.

Once you click OK, the Trigger Pattern you selected is shown in the Recording Options dialog boxv (below), and the PCIe text in the Pattern Trigger pane is displayed.

Tunneled PCIe Packet

Check this option if you are trying to trigger on a PCIe TLP. In the special case of PCIe tunneling, the pattern being set for matching is applied simultaneously to the following DWORDS:

• DWORD0-DWORD1-DWORD2-DWORD3-DWORD4

• DWORD0-DWORD3-DWORD4-DWORD5-DWORD6

The above compensates for the fact the PCIe can insert a 2-DWORD DLP at the beginning of a tunneled packet, causing the PCIe TLP to start at DWORD 3.

The other Packet Types chosen from the drop down menu function in a similar manner.

TLP Range Trigger

This allows you to trigger on TLPs that match specific ranges of PDF, Supplemental ID, HopID, and Length. You can choose to trigger if one or all of the defined conditions occurs.

CL_WAKE Trigger

Allows triggering on CL_WAKE packets with specific re-timer indexes.

Sideband Pattern Trigger

This is used on SideBand traffic to trigger up to 4 DWORDS of pattern matching.

Trigger Enabled: This turns the triggering off or on based on the defined pattern. The pattern can be preserved in either the triggering mode or with it turned off.

Copy from Right/Copy from Left: To simplify setting patterns you want to match from either transmitter, click on this button to copy the pattern from the OTHER side to the current one.

The SB pattern trigger definition provides both Quick and Detailed options. In Quick mode, the software displays a list of SB packet fields with allowed options for each field based on the latest USB4 specification. The image below shows editing SB pattern trigger in Quick mode.

Choose the Detailed mode to define the desired pattern based on sequence of DWORD match/mask. This option allows you to define any customized pattern that not possible through standard field definitions. The image below shows editing SB patterns in Detailed mode.

Click Edit to display a new window so you can edit match/masks to define a desired pattern. The image below shows SB patterns.

Filters Pane

Filter Out Pane

Select the items you do not want captured in the trace file. This reduces the size of the trace file and/or reduces the amount of capture memory used.

TS PRBS/PRTS allows for filtering out the PRBS11 (in case of TS1) or PRTS7 (in case of TS2, TS3, and TS4) portion of Gen 4 Training Sequences. Only the headers are retained in the capture.

When you select TLP Filtering from the Filter Out tab, these options appear:

Using this window, you can define Filter IN (capture only TLP traffic with associated HOP ID(s)) criteria or Filter Out (do not capture TLP traffic with associated HOP ID(s)) criteria separately for left/right port. There are options to swap left/right patterns or copy pattern from other side for quicker pattern definition.

You can also use the Copy from Right and Copy from Left buttons to simplify editing the options.

In Filter Out mode, when Do not filter packets with header gap error is checked, it keeps TLP packets in trace with a header GAP violation.

This allows you to filter out TLPs that match specific ranges of PDF, Supplemental ID, and HopID.

Individual Lane Triggering

Select this checkbox to allow triggers to be configured on a per-lane basis.