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怎么控制约束net上的pin pair

时间:10-02 整理:3721RD 点击:

Hi all,

 In my FPGA-DDR2 design, on the net of A8, there is a pullup resistor. Please refer the attached pix for the layout on my board.

The path I need to control prop delay is from FPGA to DDR2. But in Allegro, pin pairs on this net is R-FPGA or R-DDR2, as following from information on this net:

            < NET >             

  Net Name:            DDR2_A8
  Member of Bus:       DDR2_ADDR

  Pin count:              3
  Via count:              2
  Total etch length:      1582.389 MIL
  Total manhattan length: 1652.899 MIL
  Percent manhattan:      95.73%

  Pin                     Type      SigNoise Model        Location
  ---                     ----      --------------        --------
  U2.T29                  BI        CDSDefaultIO          (5652.756 3039.055)
  P2.93                   IN        CDSDefaultInput       (6383.000 2921.728)
  RP8.1                   UNSPEC    DEFAULT_RESISTOR_PACK_4_47OHM (6899.800 2633.200)

  No connections remaining

  Properties attached to net
    LOGICAL_PATH      = @\penguin-1\.schematic1(sch_1):ddr2_a8
    FSP_NET           = DDR2_A<0>
    BUS_NAME          = DDR2_ADDR

  Electrical Constraints assigned to net
    prop delay: from AD to AR  min=1600.000 MIL  max=2200 ns
    relative prop delay: global group DDR2_ADDR_CTRL_CLK from AD to AR  delta=0.000 MIL  tol=280.000 MIL
    max parallelism: 300 MIL length at 6 MIL separation
    max parallelism: 600 MIL length at 7 MIL separation
    max parallelism: 1000 MIL length at 8 MIL separation
    max parallelism: 2000 MIL length at 10 MIL separation
    FSP_NET: DDR2_A<0>

  Constraint information:
    (Dly) RP8.1 to U2.T29  max= 2200ns  actual= 1447.605 MIL  (0.235986ns)
            (6899.800,2633.200) pin RP8.1,UNSPEC,TOP/TOP
      767.468 MIL (0.114477ns) cline TOP
            (6258.000,2898.109) via TOP/BOTTOM
      652.3 MIL (0.117235ns) cline SIG4
            (5672.440,3058.740) via TOP/BOTTOM
      27.838 MIL (0.00427453ns) cline TOP
            (5652.756,3039.055) pin U2.T29,BI,TOP/TOP

    (Dly) RP8.1 to P2.93  min= 1600 MIL  actual= 902.251 MIL
            (6899.800,2633.200) pin RP8.1,UNSPEC,TOP/TOP
      767.468 MIL cline TOP
            (6258.000,2898.109) via TOP/BOTTOM
      134.783 MIL cline BOTTOM
            (6383.000,2921.728) pin P2.93,IN,BOTTOM/BOTTOM

    (RDly) RP8.1 to U2.T29  min= 2056.43 MIL  max= 2616.43 MIL  actual= 1447.605 MIL
                   target=  (DDR2_CKE0) RP5.2 to U2.U31
            (6899.800,2633.200) pin RP8.1,UNSPEC,TOP/TOP
      767.468 MIL cline TOP
            (6258.000,2898.109) via TOP/BOTTOM
      652.3 MIL cline SIG4
            (5672.440,3058.740) via TOP/BOTTOM
      27.838 MIL cline TOP
            (5652.756,3039.055) pin U2.T29,BI,TOP/TOP

  Member of Groups:
    MATCH_GROUP     : DDR2_ADDR_CTRL_CLK
    BUS             : DDR2_ADDR
    PHYSICAL & SPACING NETCLASS: 8MIL

Can anybody give me some advice to make control on the path from FPGA to DDR2?

Thanks!

如果你的net接线是FPGA-->R.1--R.2-->DDR2这种模式你可以建立Xnet形式,就会产生FPGA到DDR2的pin pair了,

如果你的net接线是FPGA-->DDR2-->R.1--R.2(上拉是接电源,下拉是接地)这种模式,你可以在constraint manager里面直接产生FPGA到DDR2的pin pair

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