Forums

How to? On LPC2106 et al, use P0.22..31 while JTAG enabled

Started by stevec April 16, 2010
How to? On LPC2106 et al, use P0.22..31 while JTAG enabled

As best as I can determine, there's no way to use the most signficant bits in the GPIO (P0) if the primary JTAG is enabled enven though the secondary JTAG is not in use.

Yes?

An Engineer's Guide to the LPC2100 Series

As long as the primary JTAG is enabled, the most significant bits (P0.22..31) are enabled for the Embedded Trace Module (ETM).
The only way to get more useable pins is to activate the secondary JTAG on P0.27..31. Doing this allowes you to use P0.0..26 as GPIO or the respective alternative function.
----- Original Message -----
From: stevec
To: l...
Sent: Saturday, April 17, 2010 4:31 AM
Subject: [lpc2000] How to? On LPC2106 et al, use P0.22..31 while JTAG enabled

How to? On LPC2106 et al, use P0.22..31 while JTAG enabled

As best as I can determine, there's no way to use the most signficant bits in the GPIO (P0) if the primary JTAG is enabled enven though the secondary JTAG is not in use.

Yes?
Thanks for the reply.
My goal of course is to use some of these msb's in P0 for I/O while using JTAG. So in understanding what was said below... if my code enables the secondary JTAG, can P0.22-26 be used as GPIO? I'm confused on this- would I be able to set those pin functions using the PIN register despite having the secondary JTAG enabled. Frankly, I don't know anything about ETM nor those signal names on 22-26.

Regards
steve

--- In l..., "Kai F." wrote:
>
> As long as the primary JTAG is enabled, the most significant bits (P0.22..31) are enabled for the Embedded Trace Module (ETM).
> The only way to get more useable pins is to activate the secondary JTAG on P0.27..31. Doing this allowes you to use P0.0..26 as GPIO or the respective alternative function.
> ----- Original Message -----
> From: stevec
> To: l...
> Sent: Saturday, April 17, 2010 4:31 AM
> Subject: [lpc2000] How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
>
> How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
>
> As best as I can determine, there's no way to use the most signficant bits in the GPIO (P0) if the primary JTAG is enabled enven though the secondary JTAG is not in use.
>
> Yes?
>

Hi

Enabling JTAG1 will automatically enable ETM, meaning that the ETM pins can no longer be used as GPIO.

It is thus best to use JTAG2 - this can be commanded by the code since it means that the ETM pins are not activated and they can be used as GPIO.

This is rather annoying in this chip if you don't realise it when designing your first board...see http://tech.groups.yahoo.com/group/lpc2000/message/2274

Regards

Mark

--- In l..., "stevec" wrote:
>
> Thanks for the reply.
> My goal of course is to use some of these msb's in P0 for I/O while using JTAG. So in understanding what was said below... if my code enables the secondary JTAG, can P0.22-26 be used as GPIO? I'm confused on this- would I be able to set those pin functions using the PIN register despite having the secondary JTAG enabled. Frankly, I don't know anything about ETM nor those signal names on 22-26.
>
> Regards
> steve
>
> --- In l..., "Kai F." wrote:
> >
> > As long as the primary JTAG is enabled, the most significant bits (P0.22..31) are enabled for the Embedded Trace Module (ETM).
> > The only way to get more useable pins is to activate the secondary JTAG on P0.27..31. Doing this allowes you to use P0.0..26 as GPIO or the respective alternative function.
> >
> >
> > ----- Original Message -----
> > From: stevec
> > To: l...
> > Sent: Saturday, April 17, 2010 4:31 AM
> > Subject: [lpc2000] How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
> >
> >
> >
> > How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
> >
> > As best as I can determine, there's no way to use the most signficant bits in the GPIO (P0) if the primary JTAG is enabled enven though the secondary JTAG is not in use.
> >
> > Yes?
>

--- In l..., "stevec" wrote:
>
> Thanks for the reply.
> My goal of course is to use some of these msb's in P0 for I/O while using JTAG. So in understanding what was said below... if my code enables the secondary JTAG, can P0.22-26 be used as GPIO? I'm confused on this- would I be able to set those pin functions using the PIN register despite having the secondary JTAG enabled. Frankly, I don't know anything about ETM nor those signal names on 22-26.
>
> Regards
> steve
>
> --- In l..., "Kai F." wrote:
> >
> > As long as the primary JTAG is enabled, the most significant bits (P0.22..31) are enabled for the Embedded Trace Module (ETM).
> > The only way to get more useable pins is to activate the secondary JTAG on P0.27..31. Doing this allowes you to use P0.0..26 as GPIO or the respective alternative function.
> >
> >
> > ----- Original Message -----
> > From: stevec
> > To: l...
> > Sent: Saturday, April 17, 2010 4:31 AM
> > Subject: [lpc2000] How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
> >
> >
> >
> > How to? On LPC2106 et al, use P0.22..31 while JTAG enabled
> >
> > As best as I can determine, there's no way to use the most signficant bits in the GPIO (P0) if the primary JTAG is enabled enven though the secondary JTAG is not in use.
> >
> > Yes?
> Steve,

there is an old application note about the secondary JTAG. May be this helps: http://www.lpc2000.com/apnotes/apnotes.htm
Check for the "Secondary JTAG"

Bob