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

[Bruce Griffiths]

Bruce Griffiths wrote:
> 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
>
>
Correction: make that a 3 input NOR and use the output of both the first 
and second stages of the 2 bit shift register to gate the clock.

BURST = SR(0)*/SR(1)*/CLK

If one wants a burst of 10kHz pulses, invert the 10KHz signal and use 
this to clock the 2 bit gated shift register

Bruce