[time-nuts] Burst mode TADD-2 divider modification?

[Bruce Griffiths]

Bruce Griffiths wrote:
> Magnus Danielson wrote:
>> Fellow time-nuts,
>>
>> To support the kind of burst measurements I am playing around with it 
>> would be good to be able to generate bursts of transitions rather 
>> than even clocks. Depending on the counter it may be simple (say 
>> using a HP5372A) or a little more difficult (DTS 2070C).
>>
>> Creating a burst of 10 kHz transitions for 10 or 100 ms should be 
>> possible to do in the PIC code with some hacking.
>>
>> Similarly creating a burst of 5 or 10 MHz clocks for 1 ms should not 
>> be too hard by sniffing the clock after the input shaper and the 
>> enable pulse from the PIC.
>>
>> I thought I would bounce this and see if people have any ideas other 
>> than mine... anyone else interest...
>>
>> Cheers,
>> Magnus
>>
> Since an external gate is required to implement the 5/10MHz clock 
> burst it would be simpler to have a selectable pulse width for say the 
> PPS output and use this to gate either the 5MHz/10MHz or 10kHz as 
> required.
>
> Bruce
>
A simple external circuit accomplish this would use an octal gated D 
flipflop (74AC377) plus a quad NOR gate (74AC02).
For a 100ms burst every second connect 10PPS to the enable input of the 
377, clock the 377 with the 10MHz signal, wire the 377 as a 2 bit gated 
shift register with the shift register input connected to PPS and use 
the output of the second stage of the shift register to gate the 10MHz 
output using the NOR gate (remember to invert the shift register output 
first).

Bruce