Counter time base properties

[HSingh13]

I was trying to generate a 15 MHz square pulse using counter in 6251 with a duty cycle of 75%. However as I run the code, the error as in the file attached comes up.

I'm new to all this. Would anyone have any suggestions on this?

Thanks!

[Kevin_Price]

Can't say exactly without seeing the code, but here are some further clues since you're "new to all this."

1. Pulse generation depends on forming time intervals that are an integer divisor of the timebase.  The minimum divisor allowed is 2.

2. The maximum timebase available on your M-series device is 80 MHz.

3. Hence, you have a dilemma.  The closest you can get to 15 MHz is with a total divisor of 5, putting you at 16 MHz.  But you'll need a 60% duty cycle since each of the 2 intervals must use a divisor of at least 2.  To get a true 75% duty cycle, the highest frequency you can generate will come from divisors of 6 and 2 for the ON and OFF time.  So that would put you at 10 MHz.

I would venture that the error message that reports an requested "Initial Delay" of 0 is at least part of the reason for your errors.  You'll need a minimum divisor of 2 again, corresponding to a delay time of 25 nanosec.

-Kevin P