How to read and write to an upper half or a specific bit from a decimal number in Simulink?

Hi.

Can you please tell me how to read and write integer number to the upper part of the register and read and write only one bit?

I can read only the whole register as an integer, but I need only part of it (TBPHS value). Similarly, how to write integer number only to an upper-half?

For the second case, how to read and write value for PHSDIR (one bit) if I am only able to read the whole TBCTL register?

Thank you in advance.

Edit:

For reading, I can use Extract Bits block.

What to use to write to upper-half or specific bit?

Answer 1

[Andy Bartlett]

Bitwise AND, OR, XOR, NOT (aka complement), shift, ...

are the ways commonly used to set, clear, or otherwise manipulate bits within a larger container.

For example, this code is forcing the first and last bit of a variable to be set to 1, using a mask and bitwise OR.

nbits = 16;
mask = uint16( sum( 2.^[0,nbits-1] ) );
n = 5;
u = uint16( randi([0,2^nbits-1],1,n) );
y = bitor(u,mask);
for i=1:n
    fprintf('Input        %s\n',dec2bin(u(i),nbits))
    fprintf('Mask         %s\n',dec2bin(mask,nbits));
    fprintf('bitor output %s\n',dec2bin(y(i),nbits))
    fprintf('\n')
end

Input        0001011010111100

Mask         1000000000000001

bitor output 1001011010111101

Input        1111011100110011

Mask         1000000000000001

bitor output 1111011100110011

Input        1101101010001100

Mask         1000000000000001

bitor output 1101101010001101

Input        1011111110010110

Mask         1000000000000001

bitor output 1011111110010111

Input        0010011111001001

Mask         1000000000000001

bitor output 1010011111001001

So read the whole register. Perform the bitwise operations to achieve the desired change. Then write whole integer back to the whole register.

Please note the MATLAB code above is only for example of the concept. Please use Simulink Bitwise blocks, Bitset block, etc.

[Mike Buba]

Thanks