To Next Page

To Previous Page

Binary Fractions

As with integers, the results are loaded low, and the MSB is a sign extension of the seventh bit. If

this value were loaded into the accumulator, we could store the results back to memory in a

variety of ways:

• Store both low and high accumulator values back to memory. This offers maximum

detail, but has the same problems as with integer multiply.

• Store only the high (or low) accumulator back to memory. This creates a potential for

a memory littered with varying Q-types.

• Store the upper accumulator shifted to the left by 1. This would store values back to

memory in the same Q format as the input values, and with equal precision to the

inputs. How shall the left shift be performed? Here’s three methods:

− Explicit shift

− Shift on store

− Use Product Mode shifter

Correcting Redundant Sign Bit



Correcting Redundant Sign Bit



IQmath

: automatically handled

(next topic)



Q math in “C”, shift in software:

int

x,y,z;

z = ((long)x * (long)y) >> 15;

Accumulator

1 1 1 1 0 1 0 0

1 1

1 1 0 1 0 0

Redundant

Sign Bit

8 - 10 C28x - Numerical Concepts & IQmath

Texas Instruments C28 Series Student Guide

Other manuals for Texas Instruments C28 Series