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Forum: FPGA, VHDL & Verilog FSM with two clock?


von sigit k. (Company: brawijaya university) (sigit)


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hi...
i want to design FSM with to two clocks in vhdl. i want to include in y 
program clock divider. so my prosesing of program can be fast at input. 
slow at display output.. can u help me? how design it in vhdl?

von Schlumpf (Guest)


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If you want to make your design work properly on a real target and if 
you are not really familiar with VHDL, constraining, clock domains etc 
you will run into big shit, if you try it this way..

Which clock rates do you intend to have on your design?

von Lothar M. (Company: Titel) (lkmiller) (Moderator)


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> i want to design FSM with to two clocks in vhdl.
Pls. show in a short sample code how this should work.
Do you know, how FSM are implemented on hardware?

> so my prosesing of program can be fast at input.
> slow at display output.
What is "input"?
What is "fast"?
What "display"?
What is "slow"?
What do you want to do?

> can u help me?
Not until much more details are known.
What is connected to "the FSM"?
What function must be implemented in "the FSM"?


All in all:
Usually if one has a problem and one does't find a almost similar 
solution, then one is on the wrong way. And I never saw a FSM with two 
clocks...

von sigit k. (Company: brawijaya university) (sigit)


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clock input in FSM architecture divided by two..example one clock for 
10khz frequency and others 1hz frequency..so i can to select one of two 
clock for delaying display of 7 segment, cause if i use counter, i will 
count more value for looping ..like counter in microcontroller...

von Schlumpf (Guest)


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If you want to "slow down" some functionality in your design you shall 
not divide the clock or worse: switch between different clocks!

You use a single system clock (fast) and you generate different slower 
enable-signals via counter derived form this system clock via counter an 
comparator.

With this enable-signals the slower functionality ist enabled (or 
disabled)

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