Motorola MPC860 PowerQUICC User Manual page 939

36.14.3 DEMOD Applications
The DEMOD function is used in modulation. The partial FD shown in Figure 36-29 can be
used for implementations.
S Ñ W
Offset + 0 S 0 W
Offset + 2
36.15 LMS1ÐComplex CoefÞcients, Complex
Samples, and Real/Complex Scalar
The LMS1 implements a basic FIR Þlter coefÞcients update. The coefÞcients and input
samples are complex numbers, but the scalar is a real or complex number. See
Figure 36-30.
36.15.1 CoefÞcients and Input Buffers
The coefÞcient vector occupies K pairs of 16-bit entries (real and imaginary components)
in memory and C(0) is stored in the Þrst location. The input sample buffer is a circular
buffer that contain (M+1) bytes. Each sample is a pair of 16-bit entries (real and imaginary
components) and the next sample is stored in the address that follows the previous sample.
Table 36-23. LMS1 Coefficients and Input Buffers
MOTOROLA
I X
I 0
I=3 (Three Iterations)
Figure 36-29. DEMOD Modulation Example
C n 1 +
=
i
Figure 36-30. LMS1 Function
CoefÞcients
imaginary{C(0)}
real{C(0)}
imaginary{C(1)}
real{C(1)}
*
*
imaginary{C(k-1)}
real{C(k-1)}
Chapter 36. Digital Signal Processing
Part V. The Communications Processor Module
Ñ
0
C n i E
´
+ X n i Ð
Input Samples
*
*
imaginary{X(n-k+1)}
real{X(n-k+1)}
*
*
imaginary{X(n-2)}
real{X(n-2)}
imaginary{X(n-1)}
real{X(n-1)}
imaginary{X(n)}
real{X(n)}
OPCODE
01001
36-25