MATLAB: Simple 16bit signal arithmetic problem

binarydigital

Hello
I have a question about N bit signal arithmetic.
I want to calculate (16bit input 1) – (16bit input 2), but 'adder' or 'sum' block shows weird results.
The blocks subtract like this way: (assuming that the signals are 8 bits for an example)
ex) (0 0 0 1 1 1 0 0) – (1 1 1 1 1 1 1 1) = (-1 -1 -1 0 0 0 -1 -1)
Is there any way to calculate binary codes?
Should I make digital adder?

Best Answer

Addition and Subtraction blocks in simulink performs integer addition and subtraction, not bitwise.
What is your expectation for bitwise operation ?
Addition:
0 0 --> 0
0 1 --> 1
1 0 --> 1
1 1 --> ? What about carry ?
Subtraction:
0 0 --> 0
0 1 --> ? Borrow ?
1 0 --> 1
1 1 --> 0
Depending upon your expectation, you can extracts the bits from your integer and construct the logic using Logical blocks to perform the bitwise operation.
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