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Altera_Forum's avatar
Altera_Forum
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16 years ago

What do these warning mean?(VHDL)

Warning: Synthesized away the following node(s):

Warning: Synthesized away the following LCELL buffer node(s):

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le3a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le5a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le5a[12]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le3a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le5a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le5a[12]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le3a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le5a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le5a[12]"

Warning: Synthesized away the following node(s):

Warning: Synthesized away the following LCELL buffer node(s):

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le3a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le4a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le4a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le4a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le4a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le5a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le5a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult2|mult_v6t:auto_generated|le5a[13]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le3a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le4a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le4a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le4a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le4a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le5a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le5a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult1|mult_v6t:auto_generated|le5a[13]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le3a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le4a[17]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le4a[16]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le4a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le4a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le5a[15]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le5a[14]"

Warning (14320): Synthesized away node "lpm_mult:Mult0|mult_v6t:auto_generated|le5a[13]"

Do they affect the behaviour? What should I do next?

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    No, I mean that Quartus most likely reports bits, that have been discarded intentionally, by design. E.g. you have an 16x16 multiply. According to your number format, you scale the result to 16 bit, apply saturation logic to the 8 upper and cut 8 lower bits. The latter causes a warning.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Hi,FvM!

    So your mean is quartus ii may cut bits it think is not neccesary when dealing with multiply operation? And the result maybe wrong? If so,why the software remind us the result maybe wrong? Your suggestion is to check whether it is right, I think that's fussy.THanks a lot,need your reply
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    I suggest to reproduce your arithmetic by pencil and paper method and check, if all bits are preserved in the final output of your design. In my signal processing designs, I'm cutting bits everywhere.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Hi,FvM!

    Sorry,I can't follow your thoughts. What do you mean by the example "cut LSB in a fixed point multiply"?

    It seems that these dismissed intermediate signals all used to mutilply computing.In my code,I used the multiply operation in deed. I am wondering that what these lpm_mults come from and why they are synthesized away.Thanks all.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Depends on the design, if skipping of bits is intentional or not. If you e.g. cut LSB in a fixed point multiply or a similar operation, it would be intentional.