Detecting JTAG on LPC236X

Started by misterhershel March 3, 2007
I would be nice if my code could detect whether the JTAG interface is
connected. I do this now with LPC213X by looking at (PINSELECT2 &
0x4), and can control power save modes, etc.

Since the JTAG pins are dedicated on the LPC236X, there is no
PINSELECT state to view.

If RTCK is grounded, JTAG AND ETM are enabled, and a bit in
PINSELECT10 is set/cleared. However, JTAG only is enabled by
connecting a bias resistor from RTCK to ground. This doesn't affect
the bit, and doesn't even make the pin go low.

The 237X has a DBGEN pin which could possible be read, but not the 236X.

I could put the RTCK bias resistor on the board, and ground the other
end and a spare IO pin, but I've already got prototypes on my desk.

Anybody out there that's done this?

An Engineer's Guide to the LPC2100 Series

Sin ce it's not off topic, i'd like to ask one other thing.
If i'm using the LPC2368 and will not use the JTAG interface, do i have to
put all those resistors in the board or the pins are internally pulled ?

Thanks, Mauricio

On 3/3/07, misterhershel wrote:
>
> I would be nice if my code could detect whether the JTAG interface is
> connected. I do this now with LPC213X by looking at (PINSELECT2 &
> 0x4), and can control power save modes, etc.
>
> Since the JTAG pins are dedicated on the LPC236X, there is no
> PINSELECT state to view.
>
> If RTCK is grounded, JTAG AND ETM are enabled, and a bit in
> PINSELECT10 is set/cleared. However, JTAG only is enabled by
> connecting a bias resistor from RTCK to ground. This doesn't affect
> the bit, and doesn't even make the pin go low.
>
> The 237X has a DBGEN pin which could possible be read, but not the 236X.
>
> I could put the RTCK bias resistor on the board, and ground the other
> end and a spare IO pin, but I've already got prototypes on my desk.
>
> Anybody out there that's done this?
>
>
>