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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LPC2292: Boot0/Boot1 Detection on Watchdog Reset ?
2005-02-14 by alipowsky
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