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
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