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Altera_Forum
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13 years ago

Modelsim addition bug

It seems that Modelsim truncates additions inappropriately. It appears that it uses the left hand side of an assignment to truncate the result of an additiion, even if that is not the final value. In...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

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Though I sympathesise with ModelSim adding apples to bananas but the banana basket is only 8 bits so adding '1' causes overflow of basket and results in zeros which are then shifted to give zeros

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But there is no overflow in the line apple = (banana + 1'b1)>>1;

The right hand side is exactly the same.

The weird thing is that the expression "banana + 1'b1" yields different results based on the size of the left hand side.