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From: Mad I.D. on 18 Sep 2009 04:43
Hi.
I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't
work like one would expect.

I can download code to FLASH, I can start debugging, BUT every time it
comes to the first STR instruction I get "Could not stop device"
ERROR. When I don't step the code it goes to some garbage address.

I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10
connector (device is ULINK(non2)).

TCK is pulled to +3.3V with 10k resistor.

Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.

I saw on some boards that TCK is pulled down? Is this the source of my
problem ?

Ivan
From: Rich Webb on 18 Sep 2009 08:29
On Fri, 18 Sep 2009 01:43:44 -0700 (PDT), "Mad I.D." <madid87(a)gmail.com>
wrote:

>Hi.
>I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't
>work like one would expect.
>
>I can download code to FLASH, I can start debugging, BUT every time it
>comes to the first STR instruction I get "Could not stop device"
>ERROR. When I don't step the code it goes to some garbage address.
>
>I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10
>connector (device is ULINK(non2)).
>
>TCK is pulled to +3.3V with 10k resistor.
>
>Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.
>
>I saw on some boards that TCK is pulled down? Is this the source of my
>problem ?

Maybe. What other NXP ARM devices have you used? If you've been
comfortable with the 21xx-series, and basically imported your
initialization steps from working code for those chips, then you may be
missing some details that have changed with the 24xx and are not really
running with the clock speed you think you're running at. That can throw
off the JTAG link and lead to unexpected behavior.

--
Rich Webb Norfolk, VA
From: Leon on 18 Sep 2009 10:53
On 18 Sep, 09:43, "Mad I.D." <madi...(a)gmail.com> wrote:
> Hi.
> I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't
> work like one would expect.
>
> I can download code to FLASH, I can start debugging, BUT every time it
> comes to the first STR instruction I get "Could not stop device"
> ERROR. When I don't step the code it goes to some garbage address.
>
> I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10
> connector (device is ULINK(non2)).
>
> TCK is pulled to +3.3V with 10k resistor.
>
> Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.
>
> I saw on some boards that TCK is pulled down? Is this the source of my
> problem ?
>
> Ivan

You probably need more resistors on the JTAG interface - see the ARM
documentation.

Leon
From: Leon on 18 Sep 2009 10:56
On 18 Sep, 15:53, Leon <leon...(a)btinternet.com> wrote:
> On 18 Sep, 09:43, "Mad I.D." <madi...(a)gmail.com> wrote:
>
>
>
> > Hi.
> > I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't
> > work like one would expect.
>
> > I can download code to FLASH, I can start debugging, BUT every time it
> > comes to the first STR instruction I get "Could not stop device"
> > ERROR. When I don't step the code it goes to some garbage address.
>
> > I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10
> > connector (device is ULINK(non2)).
>
> > TCK is pulled to +3.3V with 10k resistor.
>
> > Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.
>
> > I saw on some boards that TCK is pulled down? Is this the source of my
> > problem ?
>
> > Ivan
>
> You probably need more resistors on the JTAG interface - see the ARM
> documentation.
>
> Leon

Sorry, it has internal pull-ups as you mentioned.

Leon
From: Tauno Voipio on 20 Sep 2009 12:55
Mad I.D. wrote:
> Hi.
> I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't
> work like one would expect.
>
> I can download code to FLASH, I can start debugging, BUT every time it
> comes to the first STR instruction I get "Could not stop device"
> ERROR. When I don't step the code it goes to some garbage address.
>
> I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10
> connector (device is ULINK(non2)).
>
> TCK is pulled to +3.3V with 10k resistor.
>
> Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.
>
> I saw on some boards that TCK is pulled down? Is this the source of my
> problem ?
>
> Ivan


IIRC, the JTAG lines should be all pulled up
with suitable resistors.

Are you sure that there is not an undesired
connection from WR- to some weird place on
the board?

Did you configure the debugger for ARM7TDMI-S?

--

Tauno Voipio
tauno voipio (at) iki fi
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