Forums

Secondary JTAG Sanity Check

Started by Richard December 16, 2004

I am planning to use the secondary JTAG (LPC2104) in a design. I
have already been debugging (from flash) using the second JTAG by
placing a firmware in flash to enable the second JTAG pins and then
starting the debugger.
So, in the actual application, I will have to load the JTAG enable
firmware everytime(via ISP)I want to debug or program via the 2nd
JTAG port, correct?
I have dip switches in the design, could I use one of these to
trigger software to write to PINSEL1 and enable the 2nd JTAG?

Thanks

Rich



An Engineer's Guide to the LPC2100 Series

Hi Richard,
- concerning 2nd JTAG I wonder if I can use the very same
JTAG ARM Adapter 2x10 Pin to connect to the 2ndary JTAG?

- If so, I can make a board without the primary JTAG and
it is still possible to debug code? Is this correct.

- I do not understand the disadvantages, if I make use of
the 2nd JTAG only. It uses less pins than the primary, and
I always need SW to enable it. Is this correct?

Best Regards
Markus Meng

Richard schrieb:

>I am planning to use the secondary JTAG (LPC2104) in a design. I
>have already been debugging (from flash) using the second JTAG by
>placing a firmware in flash to enable the second JTAG pins and then
>starting the debugger.
>So, in the actual application, I will have to load the JTAG enable
>firmware everytime(via ISP)I want to debug or program via the 2nd
>JTAG port, correct?
>I have dip switches in the design, could I use one of these to
>trigger software to write to PINSEL1 and enable the 2nd JTAG?
>
>Thanks
>
>Rich >
>Yahoo! Groups Links >
>

--
Mit freundlichen Grsen
Markus Meng

********************************************************************
** Meng Engineering Telefon 056 222 44 10 **
** Markus Meng Natel 079 230 93 86 **
** Bruggerstr. 21 Telefax 056 222 44 34 **
** CH-5400 Baden Web www.meng-engineering.ch **
********************************************************************




Marcus:

Comments next to your questions.

Regards,

Ian

--- In , Markus Meng <meng.engineering@b...>
wrote:
> Hi Richard, >
> - concerning 2nd JTAG I wonder if I can use the very same
> JTAG ARM Adapter 2x10 Pin to connect to the 2ndary JTAG?
Ian > Yes, exactly the same.

>
> - If so, I can make a board without the primary JTAG and
> it is still possible to debug code? Is this correct.
Ian > Yes, with the caveat to question three.

>
> - I do not understand the disadvantages, if I make use of
> the 2nd JTAG only. It uses less pins than the primary, and
> I always need SW to enable it. Is this correct?
Ian > The secondary JTAG is enabled by software so you cannot get
there unless you have the part FLASHed with the right code. You
cannot load a RAM based example unless the JTAG is enabled first
which means the right part of code MUST be in FLASH first. You can
of course load a small application to enable the secondary JTAG via
the serial port.

>
> Best Regards
> Markus Meng
>
> Richard schrieb:
>
> >I am planning to use the secondary JTAG (LPC2104) in a design. I
> >have already been debugging (from flash) using the second JTAG by
> >placing a firmware in flash to enable the second JTAG pins and
then
> >starting the debugger.
> >So, in the actual application, I will have to load the JTAG enable
> >firmware everytime(via ISP)I want to debug or program via the 2nd
> >JTAG port, correct?
> >I have dip switches in the design, could I use one of these to
> >trigger software to write to PINSEL1 and enable the 2nd JTAG?
> >
> >Thanks
> >
> >Rich
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
> --
> Mit freundlichen Grsen
> Markus Meng
>
> ********************************************************************
> ** Meng Engineering Telefon 056 222 44 10 **
> ** Markus Meng Natel 079 230 93 86 **
> ** Bruggerstr. 21 Telefax 056 222 44 34 **
> ** CH-5400 Baden Web www.meng-engineering.ch **
> ********************************************************************





I am wondering how this works when debugging a product through the
2nd JTAG. It seems like you could never run the code that is
already in the part as you would have to erase it and download the
bit of code to enable the 2nd JTAG. Correct?

Rich --- In , "ian48harry" <ahi93@d...> wrote:
>
> Marcus:
>
> Comments next to your questions.
>
> Regards,
>
> Ian
>
> --- In , Markus Meng
<meng.engineering@b...>
> wrote:
> > Hi Richard,
> >
> >
> >
> > - concerning 2nd JTAG I wonder if I can use the very same
> > JTAG ARM Adapter 2x10 Pin to connect to the 2ndary JTAG?
> Ian > Yes, exactly the same.
>
> >
> > - If so, I can make a board without the primary JTAG and
> > it is still possible to debug code? Is this correct.
> Ian > Yes, with the caveat to question three.
>
> >
> > - I do not understand the disadvantages, if I make use of
> > the 2nd JTAG only. It uses less pins than the primary, and
> > I always need SW to enable it. Is this correct?
> Ian > The secondary JTAG is enabled by software so you cannot get
> there unless you have the part FLASHed with the right code. You
> cannot load a RAM based example unless the JTAG is enabled first
> which means the right part of code MUST be in FLASH first. You
can
> of course load a small application to enable the secondary JTAG
via
> the serial port.
>
> >
> > Best Regards
> > Markus Meng
> >
> > Richard schrieb:
> >
> > >I am planning to use the secondary JTAG (LPC2104) in a design.
I
> > >have already been debugging (from flash) using the second JTAG
by
> > >placing a firmware in flash to enable the second JTAG pins and
> then
> > >starting the debugger.
> > >So, in the actual application, I will have to load the JTAG
enable
> > >firmware everytime(via ISP)I want to debug or program via the
2nd
> > >JTAG port, correct?
> > >I have dip switches in the design, could I use one of these to
> > >trigger software to write to PINSEL1 and enable the 2nd JTAG?
> > >
> > >Thanks
> > >
> > >Rich
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> > --
> > Mit freundlichen Grsen
> > Markus Meng
> >
> >
********************************************************************
> > ** Meng Engineering Telefon 056 222 44
10 **
> > ** Markus Meng Natel 079 230 93
86 **
> > ** Bruggerstr. 21 Telefax 056 222 44
34 **
> > ** CH-5400 Baden Web www.meng-
engineering.ch **
> >
********************************************************************