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| language:langs:sizing [2021/03/07 12:33] – [low leak addition on channel length] rajit | language:langs:sizing [2022/05/13 12:53] (current) – rajit | ||
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| The sizing sub-language is used to simplify gate sizing specifications. The [[prs|prs]] sub-language already provides a mechanism to specify sizing, but this can become very verbose. For example, consider an inverter | The sizing sub-language is used to simplify gate sizing specifications. The [[prs|prs]] sub-language already provides a mechanism to specify sizing, but this can become very verbose. For example, consider an inverter | ||
| - | < | + | < |
| prs { | prs { | ||
| in => out- | in => out- | ||
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| Now, if we want the pull-up network to have width 20 units and the pull-down to have width 10 units, this gets turned into: | Now, if we want the pull-up network to have width 20 units and the pull-down to have width 10 units, this gets turned into: | ||
| - | < | + | < |
| prs { | prs { | ||
| in< | in< | ||
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| Often all one is interested in is sizing the gates so that they have some unit drive strength, where the unit selected is technology/ | Often all one is interested in is sizing the gates so that they have some unit drive strength, where the unit selected is technology/ | ||
| - | < | + | < |
| prs { | prs { | ||
| in => out- | in => out- | ||
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| This has the same effect as: | This has the same effect as: | ||
| - | < | + | < |
| prs { | prs { | ||
| in <10> -> out- | in <10> -> out- | ||
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| The p-to-n ratio is automatically used to size the pull-up network differently from the pull-down network. | The p-to-n ratio is automatically used to size the pull-up network differently from the pull-down network. | ||
| - | < | + | < |
| prs { | prs { | ||
| a & b => c- | a & b => c- | ||
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| The example above results in the following sizing: | The example above results in the following sizing: | ||
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| prs { | prs { | ||
| a<20> & b<20> -> c- | a<20> & b<20> -> c- | ||
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| An example of the general form of the sizing directive is: | An example of the general form of the sizing directive is: | ||
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| | | ||
| out {-5,lvt,2 ; +4,lvt,2 } | out {-5,lvt,2 ; +4,lvt,2 } | ||
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| </ | </ | ||
| This says that the pull-down network should be sized with 5 times the drive strength, and all gates should use two fingers and '' | This says that the pull-down network should be sized with 5 times the drive strength, and all gates should use two fingers and '' | ||
| - | < | + | < |
| sizing { | sizing { | ||
| out {+4,lvt,2 ; -5,lvt,2 } | out {+4,lvt,2 ; -5,lvt,2 } | ||
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| If a circuit wants to use a different unit width, that can also be specified as follows: | If a circuit wants to use a different unit width, that can also be specified as follows: | ||
| - | < | + | < |
| sizing { | sizing { | ||
| unit_n <- 20; | unit_n <- 20; | ||
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| The benefits of a sizing body are best illustrated when combined with the implementation relation. Consider the following example: | The benefits of a sizing body are best illustrated when combined with the implementation relation. Consider the following example: | ||
| - | < | + | < |
| defproc inv (bool? i; bool! o) | defproc inv (bool? i; bool! o) | ||
| { | { | ||
| Line 118: | Line 118: | ||
| The default sizing equalizes drive strengths for the pull-up and pull-down network. For gates used in cyclic control logic in asynchronous design, the optimal drive strengths are different. To use the optimal ratio, you can add: | The default sizing equalizes drive strengths for the pull-up and pull-down network. For gates used in cyclic control logic in asynchronous design, the optimal drive strengths are different. To use the optimal ratio, you can add: | ||
| - | < | + | < |
| prs { | prs { | ||
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| For adding a specified additional length to the minimum length of your transistors, | For adding a specified additional length to the minimum length of your transistors, | ||
| - | < | + | < |
| prs { | prs { | ||
| in => out- | in => out- | ||
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| </ | </ | ||
| - | To configure how much is added add this line to the configuration | + | To configure how much is added add this line to the configuration |
| < | < | ||
| Line 155: | Line 155: | ||
| </ | </ | ||
| - | (The length unit here is SI units.) | + | The length unit here is absolute (i.e. not scaled), so the amount specified above is 15nm. |