I looked in the user manual for the LPC932A1 (the newer fixed up version of the device) and noted for the WDT that there is a statement that indicates that the WDT prescaler starts counting right after the WDT Feed Sequence. This is not a sure-fire indication that the pre-scaler is reset on each feed sequence but is certainly seems to imply that it is reset. Another indication is that they provide a formula for the WDT timeout period and this formula does not appear to show any count variation due to an indeterminate state of the prescaler after the WDT Feed Process.

I also looked into details about the RTC System Clock prescaler in the same users manual. There is not a definitive statement that the RTC prescaler is reset under any specific conditions. There is a rather clear indication in the Figure 19. Real-time clock/system timer block diagram that shows that the RTC_RESET SFR bit directly clears the 7-bit prescaler. The same figure shows that power on reset also puts the RTC_RESET bit to the state that resets the prescaler.

If you need information that is more detailed than this then I suggest that you will have to either contact knowledgable people at Philips or you could devise some clever software tests in order to infer the pre-scaler behaviors for the WDT and/or the RTC.

Michael Karas