Special chip..

[Jan]

Hi,


I am looking for a chip that will generate a clock pulse with a frequency that I can adjust digitally.(8 bits?)


The frequency range should be from 60Hz(16ms) to 1kHz(1ms).


It should increase with 1ms increments.


I have a solution with VCO and DAC, but perhaps there is a standard chip.


Anyone know of such a chip ?


Regards, Jan

[Joe Rutsky]

Re: Special chip..

Ever try programming a microcontroller to do this?


You should be able to do this in a pic 12c508,9.


It is small but has the capability to do this and you could even do it using the onboard clock so there is no need for external crystal. You could program up/down buttons to adjust the period of the signal. If you get a serial lcd, you could even have it display the current period/frequency.


Joe

[Jan]

Re: Special chip..

Hi Joe,


It is controlled by a PIC16F84. (sends the digital data)


As far as I know I cannot set the PIC processor to contineously pulse on a pin and meanwhile run the program.


As I understood, it will first pulse x times and then continue with program ..


Is this correct ?


Regards, Jan

[Jan]

Re: Special chip..

Joe,


I had a look at my flowchart again and it turns out that during the time I need these pulses the program is in a waitloop anyway... waiting for these pulses to finish


That means I can use your suggestion which will drop 7(!) chips (=50%) in my design.


So, your suggestion helped greatly... I tried to make it to difficult.


Thanks, Jan

[Joe Rutsky]

Re: Special chip..

You could start the program and the frequencies that you stated should leave plenty of overhead in the chip to do other things in between transitions. You could use the interrupt timer but it takes a little overhead to sense the interrupt although I don't think enough to make a difference. You would set a variable equal to the number of interrupts to you need to get to the value you want and then increment a counter for each interrupt. Compare your counter to the number of interrupts and when it matches, change the transition (low to high or vice versa).


Joe