[time-nuts] Can (will) a M12+T generate a negative sawtooth message ?
EWKehren at aol.com
EWKehren at aol.com
Sun May 18 20:55:49 EDT 2014
I think there is confusion between where there is a negative delay. Yes the
M12 can have a negative value but in order to correct for the full range
of the saw tooth at zero the DS chip has to add 128 nsec delay plus the zero
value. Depending on the message it ads or subtracts from that value. As
saw teeth get smaller there are chips with .25 and .5 nsec. steps. Later GPS
units have messages with higher resolution steps.
Bert Kehren
In a message dated 5/18/2014 8:26:31 P.M. Eastern Daylight Time,
tvb at leapsecond.com writes:
-128 is 0x80
+127 is 0x7F
If in doubt, just look at the sawtooth correction messages coming out of
your M12.
/tvb (i5s)
On May 18, 2014, at 4:17 PM, Chris Albertson <albertson.chris at gmail.com>
wrote:
>> Chris,
>>
>> The manual clearly states -128 to +127. What's your problem with that?
>
> Yes it gives that range. It says the value is stored in 8 bits.
>
> But how is it stored? Certainly not as sign bit and 7 bit magnitude
> or you could not have -128. They don't say but options are either
> an assumed bias of -128 or twos complement. I bet it's an assumed
> bias.
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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