[time-nuts] Garmin GPS12XL V3.51

[Leo Bodnar]

Assume that the device does not have any reliable long term non-volatile memory that you can update.
In the absence of any clues your only reliable piece of knowledge is that the cold start date is somewhere after the date of manufacturing or, most often, firmware compilation date.
This is the simplest strategy - one that provides 20 years of device lifespan.  "Device" in this case can be anything, including a single chip module that only has mask ROM and 128bytes of OTP memory like most Ublox modules.

If you have NVRAM, you can store last seen full week number periodically.  Unless you don't power up the device for 20 years since last update you should be fine too.

Of course, if you have the ability to decode CNAV messages you can kick the can much further down the road.
Leo

> From: Joe Leikhim <jleikhim at leikhim.com>
> My question is this. Why would the receivers be hard coded to a start date for the 1023 week register?
> Why doesn't the receiver restart that date whenever reset or turned on after a period of time?
> It seems like faulty logic to build in a defect like this.