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 Delay Tune for beginner 

Last post Mon, Oct 21 2013 6:02 AM by mcatramb91. 17 replies.
Started by binpersonal 15 Oct 2013 12:18 PM. Topic has 17 replies and 3205 views
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  • Tue, Oct 15 2013 12:18 PM

    Delay Tune for beginner Reply
    Dear all, when I use manual delay tune in Allergo 16.3, why there are two numbers on the right hand side corner as the following figure?

    Which number should I use?   And what are the meaning of  "total manhattan length" ?  Where I can find tutorials for dealy tune for 16.3?

      Net Name:            CH6
      Pin count:              4
      Via count:              3
      Total etch length:      13388.442 MIL
      Total manhattan length: 6524.945 MIL
      Percent manhattan:      205.19%

      No connections remaining

      Properties attached to net
        LOGICAL_PATH      = @mux_debug_brd.schematic1(sch_1):ch6
        NO_ROUTE
        ELECTRICAL_CONSTRAINT_SET  = CH0_U5

    Electrical Constraints assigned to net
    prop delay: from AD to AR  min=13400.000 MIL  max=13405.000 MIL

    Thank You very much!
    • Post Points: 20
  • Thu, Oct 17 2013 7:55 AM

    • oldmouldy
    • Top 10 Contributor
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    Re: Delay Tune for beginner Reply
    The figure didn't get attached correctly but I guess that is the "heads-up" display, the value will be the current delay, the "bar" will be red to the left, less than the "min" value, and red to the right, greater than the "max" value, and green in the middle to match. You are trying to tune the length to be between the two limits. At present, the length is 13388.442 mils which is below the "min" requirement of 13400 mils by about 12 mils. You can ignore the Manhattan Length for the purposes of delay tuning, this is just the orthogonal distance between the ends of the route (for example: North / South, then East / West to get from one pin to the other)
    • Post Points: 20
  • Thu, Oct 17 2013 8:13 AM

    Re: Delay Tune for beginner Reply

    Thanks,

     It displays " Dly -3161.751     +67.442"  when I use the "delay tune".

    Why the first value is negative? 

    • Post Points: 5
  • Thu, Oct 17 2013 2:35 PM

    Re: Delay Tune for beginner Reply

    Also my status bar is always red, it didn't turn green,  is there any setting I need to do to make it work?

    For example: when the status bar display "Dly -3508.416  +15.38", I got the etch length is 13001.38, with the range of my constraints,

    But the status bar didn't turn green, it is still red, and not in the middle either.  The two Dly values doesn't help me either. What should I do? 

    Thanks!

     
    LISTING: 1 element(s)

                  < NET >              

      Net Name:            CH34

      Pin count:              4
      Via count:              1
      Total etch length:      13001.38 MIL
      Total path length:      16103.443 MIL
      Total manhattan length: 4995.197 MIL
      Percent manhattan:      322.38%

      Pin                     Type      SigNoise Model        Location
      ---                     ----      --------------        --------
      U7.21                   UNSPEC                          (948.630 1193.701)
      U7.25                   UNSPEC                          (948.630 1170.079)
      T34.1                   UNSPEC                          (1193.063 -455.000)
      J1.24                   UNSPEC                          (617.500 -2981.500)

      1 unrouted connection(s) remaining
        T34.1 to J1.24

      Properties attached to net
        LOGICAL_PATH      = @mux_debug_brd.schematic1(sch_1):ch34
        NO_ROUTE
        ELECTRICAL_CONSTRAINT_SET  = CH2_U7

      Electrical Constraints assigned to net
        prop delay: from AD to AR  min=13000.000 MIL  max=13005.000 MIL

     

    • Post Points: 20
  • Fri, Oct 18 2013 5:56 AM

    • chads108
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    Re: Delay Tune for beginner Reply

    It appears that you haven't finished routing the net in your last post.  I don;t think you can actually get the length of tye net to be within your specs if it is not completely routed.

    • Post Points: 20
  • Fri, Oct 18 2013 7:37 AM

    Re: Delay Tune for beginner Reply

    Thanks, for finished routing, the status bar doesn't turn green either, always red:

    Net Name:            CH6
      Pin count:              4
      Via count:              3
      Total etch length:      13388.442 MIL
      Total manhattan length: 6524.945 MIL
      Percent manhattan:      205.19%

      No connections remaining

      Properties attached to net
        LOGICAL_PATH      = @mux_debug_brd.schematic1(sch_1):ch6
        NO_ROUTE
        ELECTRICAL_CONSTRAINT_SET  = CH0_U5

      Electrical Constraints assigned to net
        prop delay: from AD to AR  min=13400.000 MIL  max=13405.000 MIL

    • Post Points: 20
  • Fri, Oct 18 2013 8:19 AM

    • chads108
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    Re: Delay Tune for beginner Reply

    Your last post shows that the routed net is 13388.442MIL which is not within the constraints you have set, so I would expect it to be red.  Are you saying that when you try to tune the net it will not come in to compliance with the constraint?  What does the DRC say?

    • Post Points: 20
  • Fri, Oct 18 2013 9:45 AM

    Re: Delay Tune for beginner Reply

     Thanks, somehow the status bar doesn't turn green, it alwasy read even when the routed net is within the constraints (as the following exmaple). There are 3 panels on the status bar, either the left one is red, with "Dly" and a negative value

    or the middle one is red with "Dly  a negative value and a positive small value"

    The color jumps between left and right panel of the status bar, it just didn't turn green and stay in the middle.

    The DRC somhow displayed part of the net ( not the whole net) as error:

     

    LISTING: 1 element(s)

                  < NET >             

      Net Name:            CH36

      Pin count:              4
      Via count:              1
      Total etch length:      13003.434 MIL
      Total manhattan length: 4974.331 MIL
      Percent manhattan:      261.41%

      Pin                     Type      SigNoise Model        Location
      ---                     ----      --------------        --------
      J1.28                   UNSPEC                          (567.500 -2981.500)
      T36.1                   UNSPEC                          (1193.063 -1111.000)
      U7.42                   UNSPEC                          (995.874 1122.835)
      U7.33                   UNSPEC                          (972.252 1146.457)

      No connections remaining

      Properties attached to net
        LOGICAL_PATH      = @mux_debug_brd.schematic1(sch_1):ch36
        NO_ROUTE
        ELECTRICAL_CONSTRAINT_SET  = CH2_U7

      Electrical Constraints assigned to net
        prop delay: from AD to AR  min=13000.000 MIL  max=13005.000 MIL

     

     


               < DRC ERROR >          

      Class:           DRC ERROR CLASS
      Subclass:        ALL
      Origin xy:       (1193.063 216.000)
      Constraint:      Propagation Delay
      Constraint Set:  CH2_U7
      Constraint Type: NET ELECTRICAL CONSTRAINTS

      Constraint value: AD:AR:13000.000 MIL:13005 mil
      Actual value:     7488.29 MIL

      - - - - - - - - - - - - - - - - - - - -
      Element type:    SYMBOL PIN
      Class:           PIN

      PIN:          J1.20
      pinuse:       UNSPEC
      location-xy:  (667.500 -2981.500)
      part of net name:  CH32
      - - - - - - - - - - - - - - - - - - - -
      Element type:    SYMBOL PIN
      Class:           PIN

      PIN:          T32.1
      pinuse:       UNSPEC
      location-xy:  (1193.063 216.000)
      part of net name:  CH32
      - - - - - - - - - - - - - - - - - - - -

    • Post Points: 35
  • Fri, Oct 18 2013 10:36 AM

    • chads108
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    Re: Delay Tune for beginner Reply

    It appears that you are using Min/Max Propagation Delay in your design.  We usually use Relative Propagation Delay, so I am going out on a limb here.  I assume you set up a Net Group.  How are your Pin Pairs set up?  What do the nets look like in Constraint Manager? Do the ones in spec show up as green?  I am thinking that maybe that you are going to get dual values and red until you get all the nets within spec.  I believe the + and - values are telling you what your current net is, in relation to the longest and shortest net in the group.  If I were you, I would look at Constraint Manager and find the longest net in the group and shorten it as much as possible and then work on lengthing from the shortest net in the group upward unti lall are within spec. 

    • Post Points: 5
  • Fri, Oct 18 2013 10:41 AM

    • mcatramb91
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    Re: Delay Tune for beginner Reply

    The Propagation Delay rule is defined with the Pin Pairs as AD:AR which translates to All Drivers/All Receivers.  What means that every Driver/Receiver pin pair combination will be checked to Min and Max Values, which you have set to Min=13000 MIL and Max=13005 MIL.  The Pin Pair etch length is being checked to the Min/Max values not the length of the entire net, you can see this with the results of the DRC Error as it sees the Pin Pair length as 7488.29 MIL which does not meet the requirement.

    If you open Constraint Manager and scroll down to NET CH36 you see the Pin Pairs which is being checked and may possibly find that multiple pin pairs have been generated which are all being checked to the Propagation Delay rule.

    Hope this helps,
    Mike Catrambone

    • Post Points: 20
  • Fri, Oct 18 2013 10:56 AM

    Re: Delay Tune for beginner Reply

    Thank you, Mike, You are right.

    How to set the Pin Pairs to check the length of the entire net?

     It has four options: Longest/Shorest Pin Pair
                                 Longest/Shorest Driver/Receiver
                                 All Drivers/All Receivers
                                 (clear)  

     Thank you very much!

     

    mcatramb91:

    The Propagation Delay rule is defined with the Pin Pairs as AD:AR which translates to All Drivers/All Receivers.  What means that every Driver/Receiver pin pair combination will be checked to Min and Max Values, which you have set to Min=13000 MIL and Max=13005 MIL.  The Pin Pair etch length is being checked to the Min/Max values not the length of the entire net, you can see this with the results of the DRC Error as it sees the Pin Pair length as 7488.29 MIL which does not meet the requirement.

    If you open Constraint Manager and scroll down to NET CH36 you see the Pin Pairs which is being checked and may possibly find that multiple pin pairs have been generated which are all being checked to the Propagation Delay rule.

    Hope this helps,
    Mike Catrambone

     

    • Post Points: 20
  • Fri, Oct 18 2013 11:34 AM

    • mcatramb91
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    Re: Delay Tune for beginner Reply

    I guess it depends on what you are trying to achieve, setting the Pin Pair to "Longest/Shortest Pin Pair" will probably get you close by checking the Shortest Pin Pair to the Min Value and checking the Longest Pin Pair to the Max Value.
           (I got a feeling you are not looking to check the Shortest Pin Pair to the value you have set now) 

    The pin-pair generation is driven by the Pin locations and may not be what you are looking for as it may generate a pin-pair that you don't expect.  You could define the Min Value as "0" so it won't check the Shortest Pin Pair but the Longest Pin Pair may end up too short as it will only DRC if it goes above the Max Value.  The only other way around it is to generate the Pin Pair that you want to check to the Min and Max Values.

    Alternative to using "Propagation Delay" is to use "Total Etch Length" with a Min-Max Value to check the length of the entire net, basically adds up all the connect lines and not the connect lines use to connect between pin-pairs.
           (this may be closer to what you are looking for)

    Hope this helps,
    Mike Catrambone

    • Post Points: 20
  • Fri, Oct 18 2013 11:42 AM

    Re: Delay Tune for beginner Reply

    Thanks, Mike, so it is not a good to use propogation delay?  what is the efficient way to set constraint and tune delay?  to use "Relative Propagation Delay" or "Total Etch Length"?

    I can not find any tutoriols. Do you have anyone to recommend?

    Thank you very much!

    mcatramb91:

    I guess it depends on what you are trying to achieve, setting the Pin Pair to "Longest/Shortest Pin Pair" will probably get you close by checking the Shortest Pin Pair to the Min Value and checking the Longest Pin Pair to the Max Value.
           (I got a feeling you are not looking to check the Shortest Pin Pair to the value you have set now) 

    The pin-pair generation is driven by the Pin locations and may not be what you are looking for as it may generate a pin-pair that you don't expect.  You could define the Min Value as "0" so it won't check the Shortest Pin Pair but the Longest Pin Pair may end up too short as it will only DRC if it goes above the Max Value.  The only other way around it is to generate the Pin Pair that you want to check to the Min and Max Values.

    Alternative to using "Propagation Delay" is to use "Total Etch Length" with a Min-Max Value to check the length of the entire net, basically adds up all the connect lines and not the connect lines use to connect between pin-pairs.
           (this may be closer to what you are looking for)

    Hope this helps,
    Mike Catrambone

     

     

    • Post Points: 35
  • Fri, Oct 18 2013 12:52 PM

    • chads108
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    Re: Delay Tune for beginner Reply

    You should be able to find what yu need in the Cadence Help documentation.  Look under PCB Editor => Constraint Manager.  Matched Groups is probably what you are looking for in this case.

    • Post Points: 5
  • Fri, Oct 18 2013 1:24 PM

    • mcatramb91
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    Re: Delay Tune for beginner Reply

    Sorry for the slow response - wanted to finish something else up first.


    To Length delay a single net:
        Propagation Delay: Checks delay of a Pin-Pair connections on a single net
        NOTE: It does not check the overall net length using the criteria described in my last post.

        Total Etch Length: Checks length of the entire net by adding up all the connected etch.

    To Length Match a group of nets (Match Group):
        Relative Propagation Delay: Match delay of Pin-Pair(s) connections on a group of nets
        NOTE: It does not compare the overall net length of the nets just the Pin-Pair connections.

    This is a lot to explain on a post, I know there are some conference papers out there that describe the
    details of how this works - still looking.  (If I find something I will let you know)

    Check the Cadence documentation and review the results of defining certain rules in Constraint Manager
    to help you thru it.  Take one net and change the Pin-Pair value to see how the Pin-Pairs get generated
    to better under the different Pin Pairs settings.

    Hope this helps,
    Mike Catrambone

     

    • Post Points: 5
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Started by binpersonal at 15 Oct 2013 12:18 PM. Topic has 17 replies.