Motorola MPC823e Reference Manual page 493

16.3.4.1 FIR1–REAL C, REAL X, AND REAL Y. The FIR1 function implements a basic
FIR filter with k real coefficients, real input samples, and real 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.
X(N)
{REAL}
16.3.4.1.1 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 containing M+1 bytes. Each sample is a 16-bit word 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. Each output is a 16-bit half-word and the new output is stored in
the address that follows the previous output.
COEFFICIENTS
C(0)
C(1)
C(2)
C(k-1)
2K bytes
Figure 16-13. FIR1 Coefficients and Sample Data Buffers
MOTOROLA
C(0)
{REAL}
T
C(1)
T
C(2)
T
C(K-1)
Figure 16-12. FIR1 Implementation Example
INPUT SAMPLES
x(N-k+1)
x(N-2)
x(N-1)
x(N)
M + 1 bytes
MPC823e REFERENCE MANUAL
Communication Processor Module
∑
Y(N)
{REAL}
k 1
–
∑
Y n ( ) C p ( )X n p
=
p = 0
OUTPUT
*
*
*
* Y(N-k+1)
Y(N-2)
Y(N-1)
Y(N)
N + 1 bytes
( )
–
*
*
*
*
*
*
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