[time-nuts] Rom Expansion for HP5370B

[Bruce Griffiths]

John Seamons wrote:
> I've been looking at this a bit recently.
> Pictures here: http://jks.com
>
> I run the 5370 firmware on an m6800 emulator written in C running on a Linux box.
> Reads and writes to I/O space are caught and executed on the 5370 hardware via an interface board hooked up to the m6800 processor bus.
>
> This interface board is a cheap USB to 32-bit parallel adapter card (Dimax sub-20).
> I used an evaluation board for the Analog Devices ADuM4160 USB power/signal isolator chip.
>
> The next step is to move everything to a microcontroller (e.g. SAM7X) on a card that replaces the processor board completely.
> As has been mentioned you can do all sorts of crazy, and perhaps useful, stuff at this point.
>
> ~~~
>
> I have a question about the dead time of the 5370.
> Can it be eliminated with a fast enough processor, buffering, interface, etc. or is it intrinsic to the measurement hardware itself?
>
>
>    
No, not without extensive redesign of the counter chain.
There are no latches for the counters they have to be frozen for readout.
The counters themselves can easily be replaced by an FPGA used together 
with the interpolators.

However if one triggers the interpolators too rapidly they never have 
time to phase lock.

Bruce