How can I set fist four bits of a byte to some other specific four bits?

If I have an array of nx1 and I want to set first four bits of each byte of an array to some other specific 4 bits so how to perform this using bitset command or is there any other command to perform this??

Answer 1

[Image Analyst]

You can use bitor() and bitand(). Try this demo:

% Pick a number.
value = 44
dec2bin(value)
% Let's define bits to set. 1 means set, 0 means leave alone.
bitsToSet = '00010011'
numberToOr = bin2dec(bitsToSet)
% Let's "OR" the number with our original "value"
% to get bits 4, 1, and 0 to be 1
newValue = bitor(value, numberToOr)
% Let's look at the bits of the new value.
dec2bin(newValue)

% Now clear bits 5, 3, and 1.   0 means clear, 1 means leave alone.
bitsToClear = '11010101' % 0 means clear that bit.
numberToAnd = bin2dec(bitsToClear)
% Let's "AND" the number with our new "value"
% to get bits 5, 3, and 1 to be 1
newValue = bitand(newValue, numberToAnd)
% Let's look at the bits of the new value.
dec2bin(newValue)

In the command window:

value =
    44
ans =
101100
bitsToSet =
00010011
numberToOr =
    19
newValue =
    63
ans =
111111
bitsToClear =
11010101
numberToAnd =
   213
newValue =
    21
ans =
10101

[Sana Shaikh]

Actually I want to replace the first four bits with some other four bits.

[Sana Shaikh]

if a= 10010101 in binary then I want to replace first four bits i-e 1001 with bits of my own let say 0010. How can I ?

[Image Analyst]

value = 149; % '10010101'
% Let's look at the bits of the value.
dec2bin(value)
% Zero out left 4 bits by ANDing with '0000 1111' (15)
% Set left 4 bits by ORing with '0010 0000' (32)
newValue = bitor(32,bitand(value, 15))
% Let's look at the bits of the new value.
dec2bin(newValue)

[Sana Shaikh]

well, this will work but just in this case (if I m not wrong)

[Sana Shaikh]

My prob is:

I have,

new=fi(bin2dec(shifted),0,8,0); %value of new 150738x1 embedded.fi

bits8to5 = fi(bitsliceget(new,8,5),0,4,0);

bits4to1 = fi(bitsliceget(new,4,1),0,4,0);

XORED=fi(bitxor(bits8to5,bits4to1),0,4,0);

Now I want to replace the first 4 bits(i-e from bit8 to bit5) of "new" with the XORED bits.

[Image Analyst]

Of course it works just in that case. Each time you have a new bit pattern you want to set, you have to change the numbers you AND and OR with. But that makes sense.

I don't know what your function bitsliceget is- it's not in my toolboxes.

[Sana Shaikh]

I got it. Thank you!

[Image Analyst]

If we're done, then please officially mark the answer as Accepted. Thanks.