I have 2 x M12+T , and a DS1023-100 Dallas chip.
I'm going to use the DS1023 to make sawtooth correction , but the DS is a
bit unclear.
http://datasheets.maximintegrated.com/en/ds/DS1023.pdf
1:
What is the REF output used for ?
As i read it it shows the internal delay through the chip. And can
The ref output is the minimal delay through the chip covering the input and
output pad buffers. It will vary slightly with temperature and voltage.
There are no negative delays in that sort of chip. It's just a bunch of
gates/buffers with a carefully calibrated delay. (For a negative delay,
Hi
The DS1023 will not do negative delays. Physics people would be very interested
in it if it did.
You will need to add a nominal delay of 1/2 the max DS1023 delay to the data
coming out of the M12. Also pay careful attention to which PPS the message
applies to (the most recent one or the
from page 167 of user 09feb05 version of user manual: It is an 8-bit
value n where n = negative sawtooth time error of next pulse The
value of N ranges from -128 to +127.
I think(?) it is really a value from 0 to 255 and you must apply a
bias to get the -128 to +127 range. And again this is a
As you can tell from the manual, the M12+ and the M12M will output a
signed -128..+127ns correction from the @@Hn message. In my opinion
you have to start from a fixed delay (an offset) in order to apply the
negative correction. I already have the Dallas/Maxim delay line but
still not used it.
On
On May 18, 2014, at 3:14 PM, Chris Albertson albertson.ch...@gmail.com
wrote:
I think(?) it is really a value from 0 to 255 and you must apply a
Chris,
The manual clearly states -128 to +127. What's your problem with that?
/tvb
___
time-nuts
Hal,
Yes, there are negative delays. The goal is that the physical 1PPS output is,
on average, exactly on-time. If designed right, that means as many negative
offset pulses occur as positive offset pulses. The spread gives you the RMS
value.
This is exactly what you want for a GPS timing
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
-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.ch...@gmail.com wrote:
Chris,
The manual clearly states -128 to +127. What's your problem with that?
Yes it
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
The question is what is the definition on time. Yes it will be always 140
nsec late to what the M12 calls zero. Good for a GPSDO. How ever if you want
it to relate to NIST time more hardware is needed unless you can
compensate that 140 nsec in antenna delay.
A simple solution would be a
On Sun, May 18, 2014 at 5:19 PM, Tom Van Baak (lab) t...@leapsecond.com wrote:
-128 is 0x80
+127 is 0x7F
So it's twos complement to negate a number you invert all the bit
then add one.
The fun part of 2's complement is when you count in binary from -1 to +1
-1 =
0 =
+1 = 0001
The
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