[time-nuts] Questionable question about the Lucent RFTGs

Bob Camp kb8tq at n1k.org
Thu Dec 4 17:52:48 EST 2014


You need the FPGA to do the timing. A CPU / MCU is not fast enough or deterministic enough to do that. By today’s standards, that’s a small FPGA. 

The HP guys did not like to do assembly code if they could avoid it. The “lots of CPU” (for the day) let them run things like Forth. Again, these days that CPU is MCU sized. 

The next layer to all this is that they did a fairly fancy approach to the disciplining process. With SA enabled on GPS, they had to do more than you would have to do today. That more involved filtering (and hardware) is part of what makes them a pretty good box, even today.


> On Dec 4, 2014, at 3:03 PM, Doug Ronald <doug at dougronald.com> wrote:
> I have sort of a dumb question about the Lucent KS-24361 RFTGs. Why do you suppose there is so much compute power in these units? They have the Xilinx FPGA, and the 68000 CPU just to discipline a 5 MHz oscillator? There must be more going on with these devices than meets my eyes.
> Thanks anyone,
> -Doug W6DSR
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