Power sequencing connecting JTAG/Wiggler ?

Development Boards MicroMod
1

Hi all,

I am wondering (please excuse me for the dumb question, and yes, I have googled it…): what is the recommended powering/connection sequence for a Wiggler (compatible, OLIMEX) JTAG dongle?

Some options that come to one’s mind:

  1. Apply power to the target board. Connect Wiggler. Connect parallel cable.

  2. Connect Wiggler. Apply power to board. Connect parallel cable.

  3. LART says: “Connect a parallel cable to you computer’s printer port, connect the JTAG dongle to the cable. Connect the other end of the JTAG dongle to the LART. Powerup the LART”

  4. ALTERA says “Attach the ByteBlasterMV download cable to a parallel port on your PC and insert the 10-pin female plug into the prototype system containing the target device […]. Note: The board must supply power to the ByteBlasterMV download cable.”

I would prefer not to connect power carrying lines (as would be the case in option 3) to non-powered device, as this might damage the device.

As for option 1, the exact sequence of events wrt power is unclear, as the JTAG connector’s power lead may actually be make contact after some pins have already been connected to a power carrying output on the target board (this assumes the Wiggler is powered from the target board, of course).

Option 4 is close to 3, with option’s 1 reservations.

So, am I left with option 2 - or are there any other options/recommendations?

Thanks much…

2

Option 3 is the way I do it. Plugging the Wiggler into a powered-up board can damage the ARM chip, I know someone who had this happen.

Leon

3

In #2, the Wiggler is connected to the target board before power is applied to the board, and before a connection is made to the parallel cable.

Note that in #3, Wiggler inputs are (potentially) seeing input voltage from the parallel cable - when the drivers inside have no power applied to them (assuming no power is drawn fro the parallel cable itself - and most Wiggler schematics out there do indeed confirm this).

4

sdfg352345:
In #2, the Wiggler is connected to the target board before power is applied to the board, and before a connection is made to the parallel cable.

Note that in #3, Wiggler inputs are (potentially) seeing input voltage from the parallel cable - when the drivers inside have no power applied to them (assuming no power is drawn fro the parallel cable itself - and most Wiggler schematics out there do indeed confirm this).

I don’t think it matters. I’ve never known anyone have a problem with it, anyway.

Leon