AR# 4159

Mentor Graphics/M1/A1 - Recommendations for improving Cross probing into hierarchy


When doing a Timing Simulation Using Xilinx A1.x/M1.x and using Cross Probing in the Mentor Interface, I can probe and simulate all the signals on the top level. When I push down into my design hierarchy on my original design viewpoint, I am unable to probe signals. I can probe some signals, but not all of them. When I try to probe a signal, I receive a message in the Quicksim II window similar to the following: 


Name "/in_3" not found. No selection performed. 


The Quicksim II transcript window might show an error similar to the following: 


// Error: $$add_mapped_traces returned error status at line 747 of file  

/products/idea.B4/pkgs/simv.ss5/userware/default/simv_gadget.ample within function $add_mapped_traces (from:Uims/Ample/Ample_eval 1D) 

// Error: Unable to resolve string '/in_3' to a signal or expression (from: Analysis/SimUI/Session 12) 

// Error: Unable to connect expression: '/in_3'. (from: Analysis/SimUI/Expression 07) 

// Error: Cannot resolve name reference: '/in_3'. (from: Analysis/SimUI/Expression 08)


Even though you use the following guidelines to improve Cross Probing, there will almost always be some signals that you will not be able to cross probe because of logic optimization or trimming. Please check the MAP report (*.mrp) to verify which logic was optimized and/or removed to see if this is the reason Cross probing is not working. 


NGDAnno looks at each CLB in the implementation and attempts to distribute that CLB's pin-to-pin delays across the logic that was mapped into it. There are a number of reasons why this process may not work, such as logic optimization, too much complex logic mapped into a CLB, or logic trimming. If it fails, ngdanno then finds all the logic mapped into the CLB and flattens the original design as necessary to bring all of the logic to the same hierarchy level. Then, it cuts out the logic and replaces it with a machine generated view of the CLB. 


1. After verifying the design is working in Functional Simulation, run the design through M1 using the default options, making sure that the "Implementation option" Timing tab is set for "EDIF" and the vendor set to "Mentor". Run the design in Quicksim II with Cross Probing enabled to see if Timing Simulation is working as expected. If the design does not seem to be functioning in Timing simulation, then you will have to start pushing down into the design hierarchy to try and narrow down the problem. This is where some signals may not be found when trying to cross probe back to the original design. 


2. If you are not able to cross probe signals and have verified that the logic is not removed or optimized, then more than likely this is because of design flattening that occurs when logical annotation fails. There are some steps to follow to help mitigate the problem: 

a) Make sure you have the latest software patches installed. 

b) Check the ngd2edif report file to see if any hierarchical levels have been flattened. 

c) Do not optimize across hierarchy boundaries, which means do NOT use the following MAP options:  

1) map -os (logic optimization style for speed|area|balanced) (Default is None) 

2) map -oe (logic optimization effort for normal|high) (Default is normal) 

d) Disable logic replication in MAP. 

1) Use map -l (to disable logic replication) if using command line. 

2) Using the GUI DESELECT the "Implement Option" in the "Optimize & Map" tab to Replicate Logic to Allow Logic  

Reductions.This may compromise Quality Of Results (QOR). 

The specific case of 4K carry logic driving flip-flops presents a complex delay model that ngdanno can not solve (an FG 

carry mode that uses CIN and packs both flops into the same CLB). Thus, if you employ such an adder driving a register, do  

NOT put those two elements far apart in the hierarchy. 


3. Re-run the Timing Simulation to verify if the design is working or not. The same results should occur if no design changes were made. Now you should be able to cross probe the design and debug where the problems are occurring. Make any necessary design changes. 


4. Run the modified design through M1 with the options described in Step 2, then again verify if Timing Simulation is correct. 


5. Once the design works in Timing Simulation with the options in Step 2, rerun the design through M1 without the -l (allowing Logic Replication), and verify if Timing Simulation is now working or not. 


6. Once the design works in Timing Simulation while allowing Logic Replication, the best implementation of the design will be found.  


NOTE: If Quality Of Results is not compromised when using options from Step 2, then this implementation can be used on the device.

AR# 4159
日期 05/14/2014
状态 Archive
Type 综合文章