AMIS30543 | Data-Sheet understanding Status register
Most of the data is duplicated between the registers. Both registers contain MSP[6:2].
If MSP contains 111001001 the registers (ignoring the MSB &quot;PAR&quot; bit) would look like:
SR3: 1110010
SR4: 1001001

If we line those up it's then like:
SR3: 1110010
SR4    1001001

You can now see the overlap.
So taking SR3 and shifting it left two places (sr3 &lt;&lt; 2) gives you:
SR3:   1110010
&lt;&lt;2: 111001000

Taking the lowest two bits of SR4 with &amp; 3 gives you:
SR4:   1001001
&amp; 3:   0000001

Then ORing the two results together:
SR3&lt;&lt;2: 111001000
SR4 &amp;3: 000000001
-----------------
MSP   : 111001001