help needed for a code in vhdl-I want output 8kHz and 256khz

[rekar33]

help for a code vhdl

hi
please I am beginner in VHDL and I have a project I 24MHZ input and I want output 8kHz and 256khz but I do not know how, is that someone can help me to complete this program
I have to divide by 3000 for 8kHz and then what should I 8kHz multiply for 256khz and finish this entity is clk_div
port (
clk_24MHZ: in std logic;
clk_8KHZ: in std logic;
clk_256KHZ: in std logic);
clk_div end;

 

[medra]

Re: help for a code vhdl

hi
search this forum for phase accumulator program, you will enter your input clock,output clock, and the program will generate the VHDL file for you.

I tried it , and it works well
hope that helps

 

[omara007]

help for a code vhdl

I think it's just a simple counter that divides by 96 for the 256KHz and by 3000 for the 8KHz.

 

[FvM]

Re: help for a code vhdl

I think it's just a simple counter that divides by 96 for the 256KHz

If you don't care for the difference between 250 and 256, it's O.K. A divider of 94 gives a better approximation, but still not exact.

A problem arises, if the 8 kHz signal is expected to be an integer part of the 256 kHz, or both frequencies to be exact for another reason, e.g. intended for an accurate real-time clock. In this case, there's no other solution than using an anolog PLL and multiplying the 24 MHz to 96 MHz first.

The said phase accumulator solution works as a fractional clock divider, generating an exact frequency (at least for the mean value) but involving a phase jitter, that may be unwanted, too. You can implement the required 1:93.75 divider as fractional divider directly, counting to 93 once and 94 three times, alternatingly.