Joe,
     Now I understand. We don't have to worry about having a reset pulse=20
that is too short. Go high, wait one instruction, go back low. Put this=20
in the main loop. It will always be 400ns long. Correct?
Thanks,
rich!

On 7/18/2014 6:10 AM, IVP wrote:
>> Well the PWM is out. Are you trying to say that we only need
>> the 20ns? What if we are off a little bit and the reset pulse is only
>> 19ns long. Wouldn't it be better to use a longer pulse to insure
>> that we always meet that 20ns requirement?
> The instruction cycle time is 200ns, so you can't have a pulse shorter
> than that. The shortest safest piece of code is
>
> bsf pulse
> nop
> bcf pulse
>
> which will give you at least 400ns
>
> Note the NOP in the middle. Because of the read-modify-write
> issue on the PICs without an output latch, a NOP is recommended
>
> http://www.piclist.com/techref/readmodwrite.htm
>
> And my real-world submission to the SX list
>
> http://www.piclist.com/techref/scenix/sxrmw.htm
>
> Joe

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