[time-nuts] Newbie questions

[Magnus Danielson]

Bob Camp wrote:
> Hi
> 
> I agree with you on the spec sheet and the fact that the cpu *should* extend
> the data. My observation was that it didn't do it if the input frequency was
> high enough. I tried it on a couple dozen counters built over a period of
> several years.

That would imply that only the time counter is CPU extended, but not the 
event counter. This is kind of fair, since it allows the lower 
frequencies to gather equalent amount of events as higher frequencies 
and thus similar precission achieved.

Should be a simple exercise to establish the event overflow properties.

I have not seen any detailed description of the MRC chip, but I know it 
is being used in HP5315A, HP5316A, HP5334A and HP5335A. The later two 
are "bigger" counters which includes the interpolators for 1 ns 
resolution versus the 100 ns time resolution of the simpler units when 
using the 10 MHz directly. The MRC chip tolerates 100 MHz directly, so 
for the 200 MHz (1/2) and 1,3 GHz (1/20) responses prescalers is used.

Thus, the time counter ticks at 10 MHz while the event counter ticks at 
up to 100 MHz for normal frequency measurement. For frequency 
comparision, the time counter is being used for the B channel, so it can 
tick at 100 MHz then.

Cheers,
Magnus