Lpc2000

----- Original Message ----- 
From: "James Dabbs" <jdabbs@...>
To: <lpc2000@yahoogroups.com>
Sent: Monday, July 25, 2005 8:52 AM
Subject: [lpc2000] Unreliable Secondary JTAG Connection


>I am using a Nohau JTAG ICE connected to the second port on a LPC2106.
> The emulator does not make a reliable connection to the JTAG unit on the
> chip.
>
> On my design, I have DBGSEL pulled to ground.  Right after reset, I
> execute the following code segment:
>
>  ldr  r0,=0x55400000
>  ldr  r1,=0xE002C004
>  str  r0,[r1]
>
> On my board, I connect the 20-pin JTAG header to the LPC2106 like this:
>
>  NTRST (3) -> P0.27/TRC0/TRST (8)
>  TDI (5) -> P0.30/TRC3/TDI  (15)
>  TMS (7) -> P0.28/TRC1/TMS (9)
>  TCK (9) -> P0.29/TRC2/TCK (10)
>  RTCK (11) -> RTCK (26)
>  TDO (13) -> P0.31/EXTIN0/TDO (16)
>  NRST (15) -> RST (5)
>
> Right after enabling the secondary JTAG port, I have a code loop that
> toggles an I/O pin.  I can see this happening, and then when I run the
> emulator, the toggling stops.  It doesn't reset; it just pauses
> execution.  I know this because the I/O pin doesn't go back to being an
> input.  However, the JTAG emulator is unable to "enter a debug state"
> which means it can't talk to the JTAG interface on the chip.  Every once
> in a while (twice, so far) it connects and I can debug my S/W, but 99.9%
> of the time it does not.
>
> This is essentially the same design as a different project I used last
> year, but I am having trouble with it now.
>
> Am I breaking some rule here?  Is there anything obvious in what I am
> doing that could cause this?

IIRC, the secondary JTAG is not intended for debugging. It's OK for 
programming the flash, of course.

Leon
--
Leon Heller, G1HSM
leon.heller@...
http://www.geocities.com/leon_heller 



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