Questions and Answers

General Questions

What is Passive TDR (pTDR)?

TDR
Time-domain reflectometry or TDR is the ability to measure the distance to electrical line fault based on reflections.
TDR analysis begins with the propagation of energy impulse into the system and the subsequent observation of the energy reflected by the system.
When using TDR in a serial communication bus like a CAN bus, If the bus is intact, there are no reflections and all the energy turns to heat on the terminators.
In case of a wire fault, there are reflections, who’s delay depend on the propagation speed in the wires, and the distance they traveled.
Of-the-shelf TDR tool transmits a pulse to the line, and measures the time to its reflection to estimate the distance in nanoseconds (ns) to the fault location.

Passive-TDR (pTDR)
Sital’s Passive TDR (pTDR) technology can estimate the distance to the wire fault without transmitting any signal to the bus!
pTDR derive the required information from the on-going communications on the line without disturbing the ongoing bus activity.
When there is a bus disconnection, the reflections (from the ongoing signals) distort the communication signals and change the their pulse width.
Measuring the distortion of a pulse width from its standard value provides the TDR information.
Passive TDR is the only TDR technique which does not send any signal to the bus (therefore called passive).
pTDR is being used to detect and locate wire faults such as disconnection and shorts.
Being able to run on live wires enable this technology to accurately detect and locate intermittent faults.

Understanding pTDR data in Buffalo Software

To enable TDR data view in Buffalo software, click the TDR button at the right hand side of the Bus Monitor window in the Buffalo software (visible only when running in Engineering mode).
A TDR data will be displayed on each module in the bus topology showing the current reflection value in nano seconds.
These TDR numbers, whether positive or negative represent the distortion from the normal CAN bus pulse width (2000ns) as measured per ECU.
If 2010ns was measured, then 10 will be displayed, if 1990ns was measured then -10 will be displayed.
Without a wire fault, these numbers are the reference base (ok value). When there is a fault, the TDR numbers minus the reference base provide the distance to the fault in ns. Estimated value per meter is 11 ns for double wire disconnect.
When clicking on a module (while in TDR mode) a popup dialog with the ok value, current and peak values and difference from the ok value is displayed.
For single wire disconnection the TDR values are less accurate, because the signals are highly distorted.

Sital tools, Buffalo and SpyTDR, do transmit standard CAN frames for a number of other practical reasons (reading DTCs, communicate with non flashed modules, etc..), but the pTDR technique itself is completely passive.

Testers & Software

What OS/platforms does COMposer run on?

COMposer runs on WinXP, Win7-32/64bits, Win8/8.1-32/64bits

What should be the source sub-address for my BC in COMposer?

In Mil-Std-1553, BC does not contain a sub-address, no need to set it up in  COMposer. Any settings will be ignored.

When setting a device to response as MultiRT, should the 1553 command match to the BC commands?

Yes. In MultiRT mode, the RTs listen and respond to specific 1553 command. The command includes the word count (and subaddress) and so, there must be a match.

Can the tester handle 1553 and PP194 messages in the same frame?

Yes.

How to troubleshoot the following COMposer initialization errors: TesterDll_ErrCode_FpgaUnloaded, TesterDll_ErrCode_FailToChangeSettings, FailedToOpenDevice?

Try the following:
a. Install and run the software on another machine in order to exclude pc issues.
b. Connect the tester to the PC via a powered USB hub.
c. Replace the tester’s default 2 meter USB cable with a shorter 40cm USB cable.

IP-Cores, API and code examples

Which file should be used for Arinc 429 IP-core?

“ARINC-429_*.*_API_Win32_Src.zip”

Can BRM1553 IP-Core API be used in other OS than Windows?

The BRM1553 and other IP-Cores are provided with API (set of functions) for Windows and Linux, written in native C and compiled with GCC compiler. The release includes drivers for windows only and API source code that can be compiled to other OS like VxWorks (some modification might be needed by the user)..