If you do not do multibit merge, or a combination of stage during synthesis due to the lack of physical information multibit cell merge unreasonable, it would need to do PR tool multibit merge or split.
Innovus support merge and split multibit in setOptMode controlled by the following two option:
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-multiBitFlopOpt { false| true| mergeOnly| splitOnly }
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-multiBitFlopOptIgnoreSDC {true| false}
In addition the following may also be used to control certain attribute two registers or whether to do merge split:
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dontMergeMultibit(settable): bool
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dontSplitMultibit(settable): bool
Incidentally, in the Innovus looking for an object property, can be used to dbSchema Check command, for example: looking for related keywords is multi instance attribute, use the command:
dbSchema inst *multi*
Return value such as:
Innovus different stages of support for mulitbit
P & R many sub-step, each step support mutibit operations are different, as follows:
preCTS:
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Merging improves bits per flop metric.
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Splitting improves bottleneck timing.
postCTS:
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No merging is supported currently due to the impact it may have on the clock tree.
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In Innovus 17.1 version, splitting of flops to improve bottleneck timing is supported.
postRoute :
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No merging or splitting is supported.
How to report multibit optimization results in the Innovus
In Innovus log can be seen in the following information about multibit optimization of:
However, no final summary. Proc can use the following to report, download the original script, please see References URL.
Using the methods and output:
After doing a multibit optimization, will change the name of a register, formal verification might be affected, you can command dumpMultiBitFlopMappingFile in Innovus used to dump multibit mapping file to the follow-up process with the following command can dump file:
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multi_bit_input_pin_mapping: includes multi-bit input pin mapping information
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multi_bit_mapping: Includes multi-bit optimization mapping information
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mbit.json: Includes multi-bit flop mapping attribute information