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Altera_Forum
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13 years ago

how to start a multicycle process correctly

hi, i would do a large bit subtractor with a multicycle process to relax setup timing. when i receive new data to be subtracted(A ,B), i store them in 2 registers clocked @ 100MHz. Once i have ...
Altera_Forum's avatar
Altera_Forum
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13 years ago

Thank you for your reply. I wrote here a simplified process. I do a slightly different thing.

I have 1 process that puts out 6 terms @100MHz to be subtracted (A,B,C,D,E,F).

Since i have a lot of time to do these subtraction ( A-B, C-D, E-F), i would use a single subtractor in multicycle.

So when data arrive, i store them in registers then i would start my multicycle process, (start_sub_process) the multicycle process loads data in the sub inputs (in0<= A in1 <=B) and does the subtraction (out <= in0-in1).

I repeat this for all the data until i have 3 results that i push out with a "done" singnal.

Since the start_sub_process belongs to a 100MHz process, i would expect that this path is analyzed with normal constraints.

If i apply constraints from clock enable multicycle example, this path is multicycled