J-tag connector && of electrical standardization

[jawadk]

Hi,

Is it possible to add four pairs of resistors between the debug signal lines and the connector as shown in the figure below.

Would such a connection not impair the controller's performance in terms of debugging or burning operation?

 

The desire to connect these resistors comes from a requirement to prevent the formation of unwanted currents in these lines (in terms of electrical standardization)

please take a look on the following figure:

Best Regards

JK

[JONATHAN LL]

Hi,

As Andrew says: what are you protecting from ?

What type of debugger/programmer are you using ? 

I dont think there is a need for any additional protection when programming or debugging under normal circumstances.

Regards,
Jonathan

[Natty]

Hi, 

Thank you for your answers.

JONATHAN LL said:

What type of debugger/programmer are you using ?

Jlink debugger 

JONATHAN LL said:

As Andrew says: what are you protecting from ?

The protection is from explosive environment (i.e ATEX)

An engineer with expert of standardization proposes to use the above scheme's configuration in order to protect the JTAG connections from unwanted currents in this environment. 

We receive from you the following answer:

" 

Hi ,

 

You can use a resistance below 100R. Note that BT840 must provide a power supply of 3V6(max).

 

Regards,

Paudy"

Can you please tell me which one of the two options is correct:  

100 Ohm for each line? Or pair of 100 Ohm(=200 Ohm) for each line?

Thanks

[awneil]

Sounds a bit spurious to me:  you won't be exposing the SWD outside the enclosure.

I don't see how putting a resistor in series with something which goes nowhere is going to make any difference?

If it's a worry about the wires acting as antennas, then just a series resistor isn't going to help.

On the other hand, if this person is really an expert, they should be familiar with how this is usually done - as the SWD interface is standard & defined by ARM.

[Natty]

I will check this idea deeper with the relevant person( I tried to figure it out but the information is almost only about pull up/pull down resistors between those lines "to prevent them from floating when the JTAG cable is not attached")

I found similar configuration in this forum:

https://electronics.stackexchange.com/questions/500587/terminal-resistor-function-on-jtag-smt2-schematic

but this is not our case.

Thanks a lot

[Natty]

By the way, if from any reason there will be decision to connect resistors as shown in the scheme, the maximum value is 100Ohm for each line?

Thanks  

[JONATHAN LL]

Using 100 Ohm or 300 Ohm should be fine as there is probably no major problems. The only issue that can cause a problem is that the rise and fall time will change and this could result in a slower times so maybe you have to reduce the read/write speed. As for the ATEX i cant really say if it is good enough or not as i am not familiar with the process.  You could try to use a couple of different resistor values and measure the behaviour with a logic analyser to se have it behaves.