IQmath
IQmath Approach
32
32
-
-
bit
bit
IQmath
IQmath
Approach
Approach
y =
y =
mx
mx
+ b
+ b
I8 Q24
I16 Q48
M
X
B
Y
>> 24
Align Decimal
Point Of Multiply
I8 Q24
I8 Q24
sssssssssssssssssI16 Q24
I8 Q24
I8 Q24
Y = ((i64) M * (i64) X) >> Q + B;
in C:
In the "IQmath" approach, rather then scaling the operands, which get added to or subtracted
from the multiplication result, we do the reverse. The multiplication result binary point is scaled
back such that it aligns to the operands, which are added to or subtracted from it. The C code
implementation of this is given by linear equation below:
int32 Y, M, X, B;
Y = ((int64) M * (int64) X) >> 24 + B;
The slide shows the implementation of the equation on a processor containing hardware that can
perform a 32x32 bit multiply, 32-bit addition/subtraction and 64-bit logical and arithmetic shifts
efficiently.
The key advantage of this approach is shown by what can then be done with the C and C++ com-
piler to simplify the coding of the linear equation example.
Lets take an additional step and create a multiply function in C that performs the following opera-
tion:
int32 _IQ24mpy(int32 M, int32 X) { return ((int64) M * (int64) X) >> 24; }
The linear equation can then be written as follows:
Y = _IQ24mpy(M , X) + B;
Already we can see a marked improvement in the readability of the linear equation.
C28x - Numerical Concepts & IQmath
8 - 19
Содержание C28 Series
Страница 64: ...Summary 3 16 C28x Peripheral Registers Header Files ...
Страница 78: ...Interrupt Sources 4 14 C28x Reset and Interrupts ...
Страница 218: ...Lab 9 DSP BIOS 9 22 C28x Using DSP BIOS ...
Страница 244: ...Lab 10 Programming the Flash 10 26 C28x System Design ...
Страница 273: ...Appendix A eZdsp F2812 C28x Appendix A eZdsp F2812 A 1 ...
Страница 275: ...Appendix eZdsp F2812 eZdsp F2812 Connector Header and Pin Diagram C28x Appendix A eZdsp F2812 A 3 ...
Страница 276: ...Appendix P2 Expansion Interface A 4 C28x Appendix A eZdsp F2812 ...
Страница 277: ...Appendix P4 P8 P7 I O Interface C28x Appendix A eZdsp F2812 A 5 ...
Страница 278: ...Appendix A 6 C28x Appendix A eZdsp F2812 ...
Страница 279: ...Appendix P5 P9 Analog Interface C28x Appendix A eZdsp F2812 A 7 ...
Страница 281: ...Appendix JP7 JP8 JP11 JP12 Boot Mode Select JP9 PLL Disable DS1 DS2 LEDs C28x Appendix A eZdsp F2812 A 9 ...
Страница 282: ...Appendix A 10 C28x Appendix A eZdsp F2812 TP1 TP2 Test Points ...