On 10/22/2012 07:13 AM, Tom Van Baak wrote:
Trimble and HP took different approaches on their GPSDO's.
Trimble lets you get into things and fiddle around. HP is much more a black box.
I have never seen anything that lets you "fiddle' with one of the HP units.
Hi Bob,
I'm glad you asked. True, the Trimble TSIP binary command set lets you fiddle
and the HP SCPI command set is much easier to use but more limited by
comparison. But there's also a rich under-the-hood layer on the HP units. Spend
some time with this file and you'll see what I mean:
http://leapsecond.com/museum/z3801a/z3801a-bin.txt
I explored the functionality in some detail during my hp GPSDO DAC dither
investigation some years ago. Contact me offline.
I spend time to reverse engineer it, and there is a whole bunch of
"hidden" features which isn't in the documentation. Among others, you
can get the list of the pSOS processes.
There's also a pForth in there, so if you kick the right escape sequence
you get into a Forth prompt, but I don't remember how much of the inner
gut you get through it.
There is *MUCH* more under the Z38xx hood!
I would need to have pSOS manuals for the 68k variant to get further.
The Trimble approach is a tuneable PI-based PLL. Nothing wrong with
that. HP went for the Smart Clock approach out of NIST. The Trimble
approach is a platform where the openness allowed for the customer to
adapt to its application (and alternative oscillators) while the HP
approach was to achieve a well-engineered solution. What Trimble did
right is that they tuned up the GPS receivers oscillator while HP spent
more on the control algorithms. It's not all, but a quick stab at the
differences.
Cheers,
Magnus
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