J-tag connector && of electrical standardization

RE: J-tag connector && of electrical standardization

Natty — Tue, 11 May 2021 07:42:43 GMT

Thank you

RE: J-tag connector && of electrical standardization

JONATHAN LL — Tue, 11 May 2021 06:34:32 GMT

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.

RE: J-tag connector && of electrical standardization

Natty — Mon, 03 May 2021 14:12:01 GMT

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

RE: J-tag connector && of electrical standardization

Natty — Mon, 03 May 2021 14:08:13 GMT

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

RE: J-tag connector && of electrical standardization

awneil — Mon, 03 May 2021 12:56:24 GMT

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.

RE: J-tag connector && of electrical standardization

Natty — Mon, 03 May 2021 12:38:04 GMT

Hi,

Thank you for your answers.

[quote userid="91187" url="~/f/nordic-q-a/74674/j-tag-connector-of-electrical-standardization/307902#307902"]What type of debugger/programmer are you using ?[/quote]

Jlink debugger

[quote userid="91187" url="~/f/nordic-q-a/74674/j-tag-connector-of-electrical-standardization/307902#307902"]As Andrew says: what are you protecting from ?[/quote]

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

RE: J-tag connector && of electrical standardization

JONATHAN LL — Mon, 03 May 2021 11:58:08 GMT

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

RE: J-tag connector && of electrical standardization

awneil — Mon, 03 May 2021 08:10:10 GMT

[quote userid="76096" url="~/f/nordic-q-a/74674/j-tag-connector-of-electrical-standardization"]The desire to connect these resistors comes from a requirement to prevent the formation of unwanted currents in these lines[/quote]

What do you mean by that?

Where would such current come from?