[time-nuts] GPS 18 behavior

Jim Lux jimlux at earthlink.net
Sun Jul 21 11:38:54 EDT 2013


On 7/21/13 7:15 AM, David McGaw wrote:
> The GPS-18 does NOT output 1PPS until it acquires lock.  Then the 1PPS
> stays on even if lock is lost, running from the internal crystal.  I
> have not checked, but once it reacquires lock I presume it jumps to the
> correct second.  All outputs including 1PPS are CMOS levels, so it
> drives both low and high.
>
> David
>

OK.. so my "wire or" question can be answered.. I've got a bunch of 
microcontrollers (teensy3 from pjrc)  with High Z inputs that I want to 
sync, and since the Garmin 1pps can both source and sink, a diode and 
resistor might work well.  When I don't have 1pps, I can have one of the 
modules reconfigured to be a source, with a series resistor.

Thanks all..


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