Motorola MPC823e - Page 496

Communication Processor Module
16-42 MPC823e REFERENCE MANUAL MOTOROLA
DSP
COMMUNICATION
16
PROCESSOR MODULE
16.3.4.2 FIR2–REAL C, COMPLEX X, AND COMPLEX Y. The FIR2 function implements
a basic FIR filter with k real 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.
16.3.4.2.1 Coefficients and Sample Data Buffers. The coefficients vector occupies k
16-bit half-words in memory and C(0) is stored in the first location. The sample input buffer
is a cyclic buffer that contains M+1 bytes and each input sample is two 16-bit half-words (real
and imaginary components). The new sample is stored in the address that follows the
previous sample. The output buffer is a cyclic buffer containing N+1 bytes. Each output is
two 16-bit half-words (real and imaginary components). The new output is stored in the
address that follows the previous output.
Figure 16-14. FIR2 Implementation Example
T
T
T
∑
X(N)
Y(N)
C(0)
C(1)
C(2)
C(K-1)
{COMPLEX}
{COMPLEX}
{REAL}
Yn () Cp () Xn p –()
p0=
k1
–
∑
=