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specify integer range and cycle through it

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drifterz

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Hi,

I wish to implement a counter with a range say from 0 to 9. Is there a way to specify the range such that it will be only within the range 0 to 9? For example, if I use counter<=counter-1
The current counter value is 0 and I wish the subtraction to yield 9 instead of -1 automatically. Likewise when counter=9, counter + 1 will yield 0.
Is there a way to do this automatically without checking for it in the code using IF? TIA
 

If you are using Verilog, you need to check the count value. Try this compact syntax:

Up counter:
count <= count == 9 ? 0 : count + 1;

Down counter:
count <= count == 0 ? 9 : count - 1;

Up/down counter:
count <= down ? (count == 0 ? 9 : count - 1) : (count == 9 ? 0 : count + 1);
 

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    drifterz

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That's what I did in VHDL.
Was just thinking whether by specifying range 0 to 9 will cause it to cycle within this range.
Found that it doesn't work this way so will have to check in the code using IF statements as above.
Thanks nonetheless.
 

It wouldn't be helpful, if a VHDL synthesis tool adds range checking to each arithmetic expression for an INTEGER variable with a range. So there is no other option than performing the range check where you need it. However you may use a function to improve readability of your code, it should be able to get the range info from variable attributes in the function body.
 

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