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How to find latency of input to output in SoC Encounter

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lien0205

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Hi guys,

I am a newbie in SoC Encounter but I need to figure out how many clock cycles for my chip to finish one calculation. So do u know if I could get this clock cycles from SoC Encounter by using any command or method?

Thank you.

Best,

Lien
 

lien0205 said:
Hi guys,

I am a newbie in SoC Encounter but I need to figure out how many clock cycles for my chip to finish one calculation. So do u know if I could get this clock cycles from SoC Encounter by using any command or method?

Thank you.

Best,

Lien
Click to expand...

Interesting question, If I understand correctly, you are writing RTL and want to figure out how many cycles you must wait until your result is ready?
I haven't written RTL myself but from rational thinking, I think, you could give the entire calculation in one clock cycle and give it to the synthesis tool.
With whatever clock you are driving this logic, you may get a negative slack on this path.
Look at the negative slack and figure out how many clock cycles it needs.

Example-
So Lets say if using a 5ns clock, you see negative slack of 9ns. Then, 9ns+5ns, the datapath would be 14ns. With a 5ns clock, you need 3 clock cycles.

If there is a better way, somebody can correct me.

Thanks,
 

huckle said:
Interesting question, If I understand correctly, you are writing RTL and want to figure out how many cycles you must wait until your result is ready?
I haven't written RTL myself but from rational thinking, I think, you could give the entire calculation in one clock cycle and give it to the synthesis tool.
With whatever clock you are driving this logic, you may get a negative slack on this path.
Look at the negative slack and figure out how many clock cycles it needs.

Example-
So Lets say if using a 5ns clock, you see negative slack of 9ns. Then, 9ns+5ns, the datapath would be 14ns. With a 5ns clock, you need 3 clock cycles.

If there is a better way, somebody can correct me.

Thanks,
Click to expand...

Thank you huckle. But what if my negtive slack is possitive? Say using 5ns clock and worst negative slack is 0.5ns. Does it mean I only need 5-0.5 ns to finish my calculation?

Lien
 

lien0205 said:
Thank you huckle. But what if my negtive slack is possitive? Say using 5ns clock and worst negative slack is 0.5ns. Does it mean I only need 5-0.5 ns to finish my calculation?

Lien
Click to expand...

Yes, then you only need 4.5ns for the path, that means one clock cycle is good.
 

huckle said:
Yes, then you only need 4.5ns for the path, that means one clock cycle is good.
Click to expand...

But the problem is I don't know how to find the total negtive slack in my chip. The only thing I could get is the worst negtive slack and how many total paths as shown below:

+--------------------+---------+---------+---------+---------+---------+---------+
| Setup mode | all | reg2reg | in2reg | reg2out | in2out | clkgate |
+--------------------+---------+---------+---------+---------+---------+---------+
| WNS (ns):| 0.109 | 0.109 | 1.000 | 0.414 | 0.297 | N/A |
| TNS (ns): | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | N/A |
| Violating Paths:| 0 | 0 | 0 | 0 | 0 | N/A |
| All Paths:|3.16e+05 |3.15e+05 | 789 | 242 | 64 | N/A |
+--------------------+---------+---------+---------+---------+---------+---------+

So do u know how could I get this total negtive slack number?

Thank you.

Lien
 

lien0205 said:
But the problem is I don't know how to find the total negtive slack in my chip. The only thing I could get is the worst negtive slack and how many total paths as shown below:

+--------------------+---------+---------+---------+---------+---------+---------+
| Setup mode | all | reg2reg | in2reg | reg2out | in2out | clkgate |
+--------------------+---------+---------+---------+---------+---------+---------+
| WNS (ns):| 0.109 | 0.109 | 1.000 | 0.414 | 0.297 | N/A |
| TNS (ns): | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | N/A |
| Violating Paths:| 0 | 0 | 0 | 0 | 0 | N/A |
| All Paths:|3.16e+05 |3.15e+05 | 789 | 242 | 64 | N/A |
+--------------------+---------+---------+---------+---------+---------+---------+

So do u know how could I get this total negtive slack number?

Thank you.

Lien
Click to expand...


You have no violating paths, which means you meet setup timing.
Total negative slack would only be anything else than zero if you had failing paths.

Hope this helps,
 

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