Motorola MPC823e - Page 504

Communication Processor Module
16-50 MPC823e REFERENCE MANUAL MOTOROLA
DSP
COMMUNICATION
16
PROCESSOR MODULE
16.3.4.4 FIR5–COMPLEX C, COMPLEX X, AND COMPLEX Y. The FIR5 function
implements a basic FIR filter with k complex coefficients, complex input samples, and
complex output. The input data is in a circular buffer with size M+1 and the output data is in
a circular buffer with size N+1. The FIR5 only uses other input data samples to implement
a fractionally spaced equalizer.
16.3.4.4.1 Coefficients and Sample Data Buffers. The coefficients vector occupies k
pairs of 16-bit half-words (real and imaginary components) in memory and C(0) is stored in
the first location. The sample input buffer is a cyclic buffer containing M+1 bytes. Each input
sample is two 16-bit half-words (real and imaginary components) and the new sample is
stored in the address that follows the previous sample. The output buffer is a cyclic buffer
that contains N+1 bytes and the new output is stored in the address that follows the previous
output.
Figure 16-18. FIR5 Implementation Example
T
T
T
∑
X(N)
Y(N)
C(0)
C(1)
C(2)
C(K-1)
{COMPLEX}
{COMPLEX}
{COMPLEX}
Yn () Cp () Xn p –()
p0=
k1
–
∑
=