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Question about circuit diagram of JTAG

POW_learn
Intellectual 550 points

Hello,

I am using a MSP430f2xxx series microcontroller... i wanted to know if there is any specific circuit diagram for the JTAG connection; i was browsing some websites where they have mentioned  pull ups on the TDI and TDO pins of the 4-wire JTAG connections.. is there any specific requirement for MSP430 devices? 

secondly, if the JTAG connector is not always hooked up to the JTAG pins, should the internal pull up or pull down resistors be enabled?

Can some1 plz help me?

thanks

  • 0
    Expert 1610 points

    You can find this information on the wiki:

    http://processors.wiki.ti.com/index.php/JTAG_%28MSP430%29

    That are only excerpts of hardware and user guides. Good starting point is here: http://www.ti.com/lit/ug/slau278h/slau278h.pdf

  • 0 in reply to Jan Kesten
    Intellectual 550 points

    I have checked that... it does not say anything about pull up or pull down resistors in any of the docs/... that's why i posted in forum

  • 0 in reply to POW_learn
    Expert 1610 points

    As far as I remember this is exactly what is used on my boards, there are no additional parts. With SBW the resistor and more the capacitor on the reset pin need some care as SBW is a very fast serial protocol and the capacitor should not be too large.

  • 0 in reply to Jan Kesten
    Guru 227245 points

    Jan said:
    With SBW the resistor and more the capacitor on the reset pin need some care as SBW is a very fast serial protocol and the capacitor should not be too large

    Alternatively, use a series resistor between RST pin and pullup resistor/pulldown capacitor). It significantly reduces the influence of the capacitor ont he SBW singal (which is tied directly to RST) but doesn't influence the effect of the capacitor for ensuring a safe startup on a slowly rising VCC (many cheap switching regulators, or a battery source that has to fill the buffer capacitors first etc). With a 1k series, you can easily use a 100nF capacitor, while without it, 2.2nF are specified as the maximum for SBW operation.

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