semi-custom /full custom

semicustom flow

i would like to get the ans for--
for analog circuits only fullcustom is use and we can't use semi-custom for it.
for digital circuits both fullcustom & semi-custom can be used
r both the statements true??
and if true give the reasons for it.

semi custom design and full custom design flow

Can you describe what do you mean by full-custom and semi-custom????

advantages of full custom digital design

semi custom : is to use already built modules instanciated from library into your design directly without making their own layout. Instead you will do the inteconnections betwen them.

Full custom : means that you are doning the work started from zero. No design no layout and you will do all the staff

I think the phrases semi-custom and full-custom for usage in analog and digital designs are correct. I didn't see a global library for analog cells until know but I beleive that every analog design team should have their own analog library at least for the basic analog blocks.

Full custom design deal with transitor metal poly .
Semi custon design deal only with metals.
Analog circuit can only be done in full custom style.

haytham said:

semi custom : is to use already built modules instanciated from library into your design directly without making their own layout. Instead you will do the inteconnections betwen them.

Full custom : means that you are doning the work started from zero. No design no layout and you will do all the staff

I think the phrases semi-custom and full-custom for usage in analog and digital designs are correct. I didn't see a global library for analog cells until know but I beleive that every analog design team should have their own analog library at least for the basic analog blocks.

Click to expand...

You are completely conflicting between reusablity concept and semi/full custom design concept.

Try to revise the Reuse Methodology Manual, and the TSMC reference flow with any EDA vendor.

Okay Omara
seems you are right. I mixed the two concepts some how.
Let me define it again
semi custom : is to use layout of already built standard cells into your layout. All what you need is to do the interconntion for theses cells.

Full custom : means to strat your layout from scratch and to build all your design layout by your self.

Am I right
Kindly correct me if you found something wrong here.

Thanks
Haytham

haytham said:

Okay Omara
seems you are right. I mixed the two concepts some how.
Let me define it again
semi custom : is to use layout of already built standard cells into your layout. All what you need is to do the interconntion for theses cells.

Full custom : means to strat your layout from scratch and to build all your design layout by your self.

Am I right
Kindly correct me if you found something wrong here.

Thanks
Haytham

Click to expand...

You are getting close

Semicustom means already prepared macros(Hard) will be used inside our presently developing layout.Rest of the design will be having standard cells.It will be used only for digital.

Full custom means developing the chip without any predeveloped macros.Mainly from transistot level.
It can be used for both digital and analog.

if I am wrong please correct me.

Tnx

This def by mani is close.

Hi,
In Full custom design we start from ground zero.
This is done all the time for Analog Design as the requirements for Analog esign are very stringent and if we want to use library components(already in the library )
then we can face many problems because there are chances that the specifications might not be met or there can be mismatch.

Where as in Digital design we donnot face such problems because the digital circuits are robust and there is rail to rail swing, also there our only concern is Power and Speed.
Theses to parameters can be optimised.
So in digital design we can use both Semi custom or full custom methodology.

Thanks
Shaikh Sarfraz

is semi-custom the same as standard cells?
anyone know what is the difference between full custom and standard cells design flow?

Added after 3 minutes:

Hi can anyone help me solve this questions?

MyChip Enterprises is seeking my teams' advice as to how best to implement their new product into an microchip. They have these questions:

1) What design methodologies should they use?
2) Would the design using either Full Custom or Standard Cells Design Flow. Compare and contrast these different design approaches?
3) They would like to use to choose a design flow that supports the design methodologies in (1). Recommend either the Full Custom or Standard Calls Design Flow. Explain how your recommendation is consistent with the design methodologies in (1).

If your design is very high performance and you know that you will not achieve that performance level with standard cells (semi-custom designing) than go for full-custom..

turtlynn said:

is semi-custom the same as standard cells?
anyone know what is the difference between full custom and standard cells design flow?

Added after 3 minutes:

Hi can anyone help me solve this questions?

MyChip Enterprises is seeking my teams' advice as to how best to implement their new product into an microchip. They have these questions:

1) What design methodologies should they use?
2) Would the design using either Full Custom or Standard Cells Design Flow. Compare and contrast these different design approaches?
3) They would like to use to choose a design flow that supports the design methodologies in (1). Recommend either the Full Custom or Standard Calls Design Flow. Explain how your recommendation is consistent with the design methodologies in (1).

Click to expand...

Added after 1 minutes:

You can also try mixed of these, like designing maximum blocks with semi-custom flow and the high performance blocks with full-custom techniques..

Semi custom : using 3rd party tools
full custom : no third party tools,

Semi-customed means all the pre-complied library is used in the final stage of design .... for example FPGA flow using the tool set Active HDL , synplify Pro and Xlinx ISE is called semi-customed flow. because we are using pre-build libraries from xlinx.
so I can tell that FPGA based flow is semi-customed flow.

And for ASIC design: final library is developed ( back - end design ) where even gate level library design ( more presice transitor lay out designs) are done and finally used is called full custom design.

please give your comment on these answers. I am close or not

with regards

Added after 3 minutes:


Hellow omara007,

If I have to make the difference between reusablity concept and semi/full custom design concept.
What can be the precise anwer for this....

thanks in advance

with regards,

gbaerf said:

so I can tell that FPGA based flow is semi-customed flow.

Click to expand...

No. FPGA flows are not semi-custom. FPGA flows are different from ASIC flows. When a designer implements his or her design on an FPGA, the FPGA tool puts the design on an already finished chip. However the design of the actual FPGA chip, before actual fabrication, usually employs the semi-custom approach. So it can be confusing...

For the ASIC flow, ASICs use different libraries, standard cell libraries, more testing, more complicated place and route, and design finishing steps.

As for the definition of semi-custom, from Chapter 1 of Introduction to VLSI Circuits and Systems by Uyemura:
"A semi-custom design is in between that of a full-custom and an ASIC-type circuit. The majority of the chip is designed using a group of primitive predefined cells as building blocks. [...] If it is not possible to meed the system specifications using the cell library then the sem-custom approach permits the designer to engineer a solution by creating alternated silicon circuits that have the desired characteristics. These are using only in small sections where the problems occur."

By ASIC-type, he means standard cell flow. So the semi-custom flow refers to a combination of standard cell library flow coupled with custom cells for a specific purpose for that design.

Full Custom: A methodology for designing integrated circuits by specifying the layout of each individual transistor and the interconnections between them.
Standard Cells: A methodology of designing Application Specific Integrated Circuits (ASICs) with mostly digital-logic features.

[Full Custom]
Advantages: - Compact designs
- Improved electrical characteristics, e.g. speed optimizations or improved frequency response

Disadvantages: - Very time consuming in the design process
- Possible to be error prone

[Standard cells]
Advantages: - Designers/ vendors can build libraries of well-tested standard cells which can be shared between users
- Good for bottom-up design

Disadvantages: - Can be time consuming to build up standard cell components
- Expensive in short-term costs but cheaper in long-term costs



Are they correct?? if wrong pls correct me.. thanks alot

different on layout and library