Hi:

I seem to have a problem getting the JTAG to work on a new LPC1765 board design. I've done numerous LPC2XXX parts and never had a JTAG problem, but this is my first time with a LPC17XX.

The TDO (pin 1) just seems to be stuck HI, never moves. I've tried PullUp or PullDn on the TCK and the rest have PullUp's. They are all 5K. The resets are both HI.

The odd thing is the TDO has 2.2V coming out of it while the Vcc is 3.30, and it has a 5K PullUp on it. That seems really strange. I have several proto boards and they all do exactly the same thing.

I know they do SWD mode too, but they are suppose to come up in JTAG mode first. Anyone run into this? Is there something special required to get the JTAG working on these LPC17XX parts?

Chris.

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Mate, The Cortex chips also use a SWD protocol for debugging, if you give
up of trying to make it to work you may get (or make your own) a cheap
CoLinkEX link board to use. This board is compatible with some IDEs.

ps: Have a Look how the Cortex decides between default JTAG and SWD
protocol, if it is controlled by the user or it is automatic detectable.
This may be your issue.

2011/12/21 sig5534

> **
> Hi:
>
> I seem to have a problem getting the JTAG to work on a new LPC1765 board
> design. I've done numerous LPC2XXX parts and never had a JTAG problem, but
> this is my first time with a LPC17XX.
>
> The TDO (pin 1) just seems to be stuck HI, never moves. I've tried PullUp
> or PullDn on the TCK and the rest have PullUp's. They are all 5K. The
> resets are both HI.
>
> The odd thing is the TDO has 2.2V coming out of it while the Vcc is 3.30,
> and it has a 5K PullUp on it. That seems really strange. I have several
> proto boards and they all do exactly the same thing.
>
> I know they do SWD mode too, but they are suppose to come up in JTAG mode
> first. Anyone run into this? Is there something special required to get the
> JTAG working on these LPC17XX parts?
>
> Chris.
>
>
>


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According to the manual, the MCU wakes up in JTAG mode and requires commands to put it into SWD mode. Is that not correct? I can't even issue commands in JTAG mode to put it into SWD mode without the JTAG mode working first.

Chris.
> ps: Have a Look how the Cortex decides between default JTAG and SWD
> protocol, if it is controlled by the user or it is automatic detectable.
> This may be your issue.
>
> 2011/12/21 sig5534 > **
> >
> >
> > Hi:
> >
> > I seem to have a problem getting the JTAG to work on a new LPC1765 board
> > design. I've done numerous LPC2XXX parts and never had a JTAG problem, but
> > this is my first time with a LPC17XX.
> >
> > The TDO (pin 1) just seems to be stuck HI, never moves. I've tried PullUp
> > or PullDn on the TCK and the rest have PullUp's. They are all 5K. The
> > resets are both HI.
> >
> > The odd thing is the TDO has 2.2V coming out of it while the Vcc is 3.30,
> > and it has a 5K PullUp on it. That seems really strange. I have several
> > proto boards and they all do exactly the same thing.
> >
> > I know they do SWD mode too, but they are suppose to come up in JTAG mode
> > first. Anyone run into this? Is there something special required to get the
> > JTAG working on these LPC17XX parts?
> >
> > Chris.
> >
> >
> >
>
>

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On 22.12.2011 11:59, sig5534 wrote:
> According to the manual, the MCU wakes up in JTAG mode and requires
> commands to put it into SWD mode. Is that not correct?

I only know the SWD protocol, not JTAG, but I can tell you that is
correct.
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I think the TDO pin is miss soldered on the LPC.

2011/12/22 Felipe de Andrade Neves

> Well, Either the problem is hardware related, or the chip JTAG circuit has
> burnt.
>
> 2011/12/22 Christopher Harvey > **
>> On 22.12.2011 11:59, sig5534 wrote:
>> > According to the manual, the MCU wakes up in JTAG mode and requires
>> > commands to put it into SWD mode. Is that not correct?
>>
>> I only know the SWD protocol, not JTAG, but I can tell you that is
>> correct.
>>
>>
>>


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