Motorola MPC823e Reference Manual page 514

Communication Processor Module
16.3.4.7 MOD–REAL SIN, REAL COS, COMPLEX X, AND REAL/COMPLEX Y. The
MOD function implements a basic modulator function with a modulation table composed of
{cos ωnT, sin ωnT} pairs, complex input samples, and real outputs. 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.
REAL Y n ( )
IMAG Y n ( )
Figure 16-24. MOD Implementation Example
16.3.4.7.1 Modulation Table and Sample Data Buffers. The modulation table is
composed of 16-bit cosine and sine pairs that occupy K+1 bytes in memory. The sample
input buffer is a cyclic buffer containing M+1 bytes. Each sample is a pair of 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 contain N+1 bytes and the new
output is stored in the address that follows the previous output. The output buffer can be real
or complex, depending on the X bit in the function descriptor.
MODULATION TABLE
sin q
1
cos q
1
sin q
2
cos q
2
*
*
sin q
n
cos q
n
K + 1 bytes
Figure 16-25. MOD Table and Sample Data Buffers
16-60
X(n)
{COMPLEX}
cos ωnT, sin ωnT
{REAL}
{ } REAL X n ( ) { } ×
cos
=
{ } REAL X n ( ) { } ×
sin
=
INPUT SAMPLES
*
*
imag {x(n-k+1)}
real {x(n-k+1)}
*
imag {x(n-2)}
real{x(n-2)}
imag{x(n-1)}
real{x(n-1)}
imag{x(n)}
real{x(n)}
M + 1 bytes
MPC823e REFERENCE MANUAL
Y(n)
{REAL OR COMPLEX}
ωnT IMAG X n ( ) { } × ωnT
– sin
ωnT { X n ( ) } × ωnT
+ IMAG cos
OUTPUT (REAL)
*
*
*
real{Y(n-K+1)}
*
*
real{Y(n-2)}
real{Y(n-1)
real{Y(n)}
N + 1 bytes
OUTPUT (COMPLEX)
*
*
*
imag{Y(n-k+1)}
real{Y(n-k+1)}
*
*
imag{Y(n-2)}
real{Y(n-2)}
imag{Y(n-1)}
real{Y(n-1)}
imag{Y(n)}
real{Y(n)}
N + 1 bytes
MOTOROLA