This example shows how to implement bit-shift operations using the MCode block. Shift operations are accomplished with multiplication and division by powers of two. For example, multiplying by 4 is equivalent to a 2-bit left-shift, and dividing by 8 is equivalent to a 3-bit right-shift. Shift operations are implemented by moving the binary point position and if necessary, expanding the bit width. Consequently, multiplying a Fix_8_4 number by 4 results in a Fix_8_2 number, and multiplying a Fix_8_4 number by 64 results in a Fix_10_0 number.
The following shows the
xlsimpleshift.m file which specifies one
left-shift and one right-shift:
function [lsh3, rsh2] = xlsimpleshift(din) % [lsh3, rsh2] = xlsimpleshift(din) does a left shift % 3 bits and a right shift 2 bits. % The shift operation is accomplished by % multiplication and division of power % of two constant. lsh3 = din * 8; rsh2 = din / 4;
The following diagram shows the subsystem after compilation: