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Altera_Forum
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9 years ago

Adder Nightmare!

Hi All, I have been trying to create an adder array which is capable of adding three 10 bit numbers together. I have it working with unsigned numbers, but as soon as I try any signed numbers, t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

As 10-bit hex numbers 896 and -128 are identical (0x380). But as 12-bit hex numbers 896 = 0x380 and -128 = 0xF80. Are you sure your output is signed and 12 bits? What do you get if you add 511 + 511 + 511? How about -1 + -1 + -1? And how about -512 + 0 + 0?

Play with different numbers and the problem should eventually become obvious.