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LPC2292: Boot0/Boot1 Detection on Watchdog Reset ?

2005-02-14 by alipowsky

I wonder whether the PortpinsP2.26 and P2.27 (Boot0/Boot1) are only
examined during a Reset caused by the Reset Line (Pin 135) driven low,
or also in case of a watchdog reset ?.
The LPC-2292 Usermanual states to different things:

Page 85 
"External and internal Resets have some small differences. An external
Reset causes the value of certain pins to be latched to
configure the part. External circuitry cannot determine when an
internal Reset occurs in order to allow setting up those special
pins, so those latches are not reloaded during an internal Reset. Pins
that are examined during an external Reset for various
purposes are: P1.20/TRACESYNC, P1.26/RTCK, BOOT1 and BOOT0 (see
chapters Pin Configuration on page 110, Pin
Connect Block on page 126 and External Memory Controller (EMC) on page
56). Pin P0.14 (see Flash Memory System and
Programming on page 262) is exemined by on-chip bootloader when this
code is executed after reset."


Page 259:
"USAGE NOTES ON WATCHDOG RESET AND EXTERNAL START
When LPC2292/2294 is conditioned by components attached to the BOOT1:0
pins to start execution in off-chip memory, and is
programmed to enable the Watchdog Timer to reset the part if it is not
periodically serviced, care must be taken to avoid problems
due to the interaction of these features. First, the BOOT1 and/or
BOOT0 pin(s) must be biased to ground using pulldown
resistors, not transistors driven from RESET low, because RESET is not
driven low during a Watchdog Reset. Second, if either
or both of the BOOT1:0 pins are used as inputs in the application, the
application designer must ensure that the external driver
will not be enabled during an internal Reset generated by the Watchdog
Timer. (One way to do this is to use one of the CS3:0
outputs to enable the driver.) If these two conditions cannot be met,
an external Watchdog facility can be used."

From page 85 i understood that an internal Reset (= Watchdog Reset ?)
will not latch the states of the specific configuration pins.

But on page 259 just this seems to be the reason for the problem
reported ??
  
Is there a way to detect a watchdog Reset externally ?

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