Lpc2000

IIRC some external watchdog timer chips force a reset on timeout only
if their input pin is held high or low for too long a period.  If the
pin is left floating, the watchdog function is disabled.  See the TI
TPS382x family info (SLVA039 section 10).  The boot loader most likely
leaves unused GPIO pins unconfigured so they should be in their
default mode as inputs.  If that case the floating connection to the
watchdog chip should disable the timed reset function.

Good luck
-Bill Knight
R O SoftWare &
http://www.theARMPatch.com


On Mon, 17 Oct 2005 12:17:58 -0000, bdmlpc wrote:

>Hello,

>bad foul!!! I think there is no software solution (except hacking the
>philips bootloader). You could insert a single gate (NAND) into the
>/reset signal that disables /reset (=1) while P0.14 (for entering
>bootloader programming mode) is low during programming. 

>  Sten

>--- In lpc2000@yahoogroups.com, "lhaddix" <lhaddix@i...> wrote:
>>
>> Hi,
>> I'm working on an LPC2138 design and just moved
>> into ESD testing. After some ESD hits there was
>> no damage, but the processor would be left not 
>> running.
>> 
>> Implementing the internal watchdog didn't fix this.
>> 
>> Apparently there are ways to nail a 2138 with ESD
>> that must stop the processor clock and thus also
>> prevent the internal watchdog from working.
>> 
>> My solution is an external supervisor chip with a
>> watchdog function that I would keep strobed with
>> some line from the micro.
>> 
>> I know this will work because when an ESD hit 'stuns'
>> the LPC2138 I can restart it by toggling reset.
>> 
>> The problem is I want to use the internal flash loader
>> to do the factory program load for my board.
>> 
>> The flash loader will not keep my external watchdog strobed
>> and will not be able to avoid a reset as a result. So the
>> external watchdog will keep it from working.
>> 
>> Question: Does the phillips flash loader toggle and pin
>> regularly that I could use for this strobe?
>> 
>> Can I hook it somehow to make it pet the dog?
>> 
>> Any ideas?
>> 
>> Landrum
>>







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