Motorola MPC860 PowerQUICC User Manual page 924

Part V. The Communications Processor Module
36.11.1.3 FIR1 Applications
The FIR1 is used in decimation and Rx interpolation. For example, the partial FD in
Figure 36-10 can be used to implement a 2:1 decimation.
S Ñ
Offset + 0 S 0
Offset + 2
36.11.2 FIR2ÐReal C, Complex X, and Complex Y
Using the values provided in the parameter packet, the FIR2 implements a basic FIR Þlter,
shown in Figure 36-11, with K real coefÞcients, 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).
X(n)
{Complex}
36.11.2.1 FIR2 CoefÞcient, Input, and Output Buffers
The coefÞcient vector occupies K 16-bit entries in memory and C(0) is stored in the Þrst
location. The input sample buffer is a circular buffer that contains (M+1) bytes and each
input sample is two 16-bit entries (real and imaginary components). The next sample is
stored in the address that follows the previous sample. The output buffer is a circular buffer
containing (N+1) bytes. Each output is two 16-bit entries (real and imaginary components).
The next output is stored in the address that follows the previous output. See Table 36-9.
36-10
W I Ñ IALL
W I 0 1
I=3 (Three Iterations)
Figure 36-10. FIR1 Decimation Example
C(0)
{Real}
T
C(1)
T
C(2)
T
C(kÐ1)
Figure 36-11. FIR2 Function
MPC860 PowerQUICC UserÕs Manual
INDEX PC Ñ Ñ
10 1 0 0
Y(n)
å
{Complex}
k 1
å
Y n ( )
=
p
OPCODE
00001
Ð
C p ( )X n p ( )
Ð
= 0
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