Lpc2000

The bootloader does not look at the RISR register. It looks at the
WDTOF flag in WDMOD register.
Even clearing of watchdog flag in user application may not help (if
timeout is too small) because the bootloader runs before application.

If you are using the watchdog only to trigger ISP then Reinvoke ISP
command might be a better choice. This was added to 213x,214x devices. 
Restore Timer1 to reset state if your application uses it.
Refer to Table 218 on page 235 of the user manual
http://www.semiconductors.philips.com/acrobat_download/usermanuals/UM10120_1.pdf

The LPC213x/214x user manual will be updated to reflect the WTOF clear
conditions.

Regards
Philips Apps

--- In lpc2000@yahoogroups.com, "Guillermo Prandi"
<yahoo.messenger@...> wrote:
>
> My code is clearing the RISR flags at boot time by doing:
> 
> #define RSIR (*((volatile unsigned char *) 0xE01FC180))
> 
> RSIR = 0x0f;
> 
> After that, the boards still ignores P0.14 after a watchdog reset. 
> Since I cleared the watchdog reset flag, I expected the bootloader to 
> invoke ISP. Is there anything else I could do from software in order 
> to make the bootloader honor the P0.14 pin?
> 
> Guille
> 
> --- In lpc2000@yahoogroups.com, "philips_apps" <philips_apps@> 
> wrote:
> >
> > Hello Guille,
> > 
> > In case of a watchdog triggered reset, P0.14 pin is ignored by the
> > bootloader and the valid user application is executed. If valid user
> > application is not found then only isp is entered. In LPC2138 the 
> WDT
> > flag is not cleared by pin reset. POR reset clears the WDT flag. 
> What
> > you are observing is expected behavior. I am assuming that WD reset
> > happened since you have mention it.
> > 
> > Regards
> > Philips Apps
> > 
> > --- In lpc2000@yahoogroups.com, "Guillermo Prandi"
> > <yahoo.messenger@> wrote:
> > >
> > > Hi, I wonder if anyone has seen this before.
> > > 
> > > While developing the firmware for my LPC2138-featured board, I 
> noticed 
> > > that the bootloader is not always invoked after a reset with 
> P0.14 low. 
> > > Even when the bootloader is not invoked, the device still 
> responds to 
> > > reset.
> > > 
> > > I tested with the Philips bootloader utility, which, measured at 
> the 
> > > reset and P0.14 pins, gives me:
> > > 
> > > 1) At T+0, P0.14 goes down from 3.3V to 0V sharply.
> > > 2) At T+0, Reset starts going down from 3.3V to 0V in an RC-type 
> curve 
> > > of 750�S.
> > > 3) At T+750�S both Reset and P0.14 are now 0V.
> > > 4) At T+500 mS reset starts going up, having been effectively low 
> for 
> > > 499mS. The rising curve is also RC-type and takes about 2 mS to 
> reach 
> > > 85%.
> > > 5) At T+840 mS, P0.14 goes up sharply. This is 338 mS *after* 
> reset 
> > > went high.
> > > 
> > > By the spec, these figures should be large enough to trigger the 
> > > bootloader, and it does, except when I've been playing around 
> with my 
> > > firmware for a while (several cycles of compile+flash 
> programming, 
> > > tests, an occasional crash, watchdog triggered, etc.). When the 
> > > bootloader stops responding, the only way to regain the 
> bootloader is 
> > > by removing power.
> > > Any ideas?
> > > 
> > > Guille
> > >
> >
>