Unable to enter ISP after watchdog reset

Started by jcwren August 1, 2007
LPC2148, bootloader version 2.11. After a watchdog reset takes place,
I am unable to enter ISP mode after setting the BSL jumpers, and
pressing reset. The system heads straight into the application code,
acting as if the jumper isn't present. If I cycle power, it works
fine. I do not have a JTAG debugger attached.

I am probably failing to set or clear a register that the ISP is
checking. Anyone have any experience with this problem? I've
searched the LPC2000 archives, and if the topic exists, I'm just not
picking the right words.

Beyond the BSL line, does the bootloader have any special expectations
of the state of the system?

Thanks,
--jc

An Engineer's Guide to the LPC2100 Series

--- In l..., "jcwren" wrote:
>
> LPC2148, bootloader version 2.11. After a watchdog reset takes place,
> I am unable to enter ISP mode after setting the BSL jumpers, and
> pressing reset. The system heads straight into the application code,
> acting as if the jumper isn't present. If I cycle power, it works
> fine. I do not have a JTAG debugger attached.
>
> I am probably failing to set or clear a register that the ISP is
> checking. Anyone have any experience with this problem? I've
> searched the LPC2000 archives, and if the topic exists, I'm just not
> picking the right words.
>
> Beyond the BSL line, does the bootloader have any special expectations
> of the state of the system?
>
> Thanks,
> --jc
>

Check section 21.4 of the User Manual. "If P0.14 is sampled low and
the watchdog overflow flag is set, the external hardware request to
start the ISP command handler is ignored.".

Richard
jcwren Wrote
>LPC2148, bootloader version 2.11. After a watchdog reset takes place,
>I am unable to enter ISP mode after setting the BSL jumpers, and
>pressing reset. The system heads straight into the application code,
>acting as if the jumper isn't present. If I cycle power, it works
>fine. I do not have a JTAG debugger attached.
>
>I am probably failing to set or clear a register that the ISP is
>checking. Anyone have any experience with this problem? I've
>searched the LPC2000 archives, and if the topic exists, I'm just not
>picking the right words.
>
>Beyond the BSL line, does the bootloader have any special expectations
>of the state of the system?

There is memory retained of whether the last reset was due to a watchdog.
The BSL line is ignored in that case. It's possible you have to clear a
watchdog reset flag. I do seem to recall there was a flag you could check.

Robert
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Yah, thanks, that did the trick. I overlooked that statement about
the watchdog flag in section 21.4, and it was not crystal clear that
the WDTOF flag was writable. The register map indicates the register
is writable, but I was led astray by the comment for WDTOF that said
'(Only after external reset)', which led me to believe that the bit
could only be cleared by a reset.

Some days you're the dog, some days you're the hydrant.

--jc

--- In l..., "rtstofer" wrote:
>
> --- In l..., "jcwren" wrote:
> >
> > LPC2148, bootloader version 2.11. After a watchdog reset takes place,
> > I am unable to enter ISP mode after setting the BSL jumpers, and
> > pressing reset. The system heads straight into the application code,
> > acting as if the jumper isn't present. If I cycle power, it works
> > fine. I do not have a JTAG debugger attached.
> >
> > I am probably failing to set or clear a register that the ISP is
> > checking. Anyone have any experience with this problem? I've
> > searched the LPC2000 archives, and if the topic exists, I'm just not
> > picking the right words.
> >
> > Beyond the BSL line, does the bootloader have any special expectations
> > of the state of the system?
> >
> > Thanks,
> > --jc
> > Check section 21.4 of the User Manual. "If P0.14 is sampled low and
> the watchdog overflow flag is set, the external hardware request to
> start the ISP command handler is ignored.".
>
> Richard
>