Motorola MPC823e - Page 517

Communication Processor Module
MOTOROLA MPC823e REFERENCE MANUAL 16-63
DSP
COMMUNICATION
16
PROCESSOR MODULE
16.3.4.8.1 Modulation Table, Sample Data Buffers, and AGC Constant. The
modulation table is composed of 16-bit cosine and sine pairs that occupy K +1 bytes in
memory. The samples input buffer is a cyclic buffer containing M+1 bytes. Each sample is
a 16-bit half-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 and the new output is
stored in the address that follows the previous output. The AGC constant is in the range
-1≤ AGC≤1.
16.3.4.8.2 DEMOD Function Descriptor. The DEMOD function descriptor bit table is
described below.
MODULATION TABLE INPUT SAMPLES OUTPUT (COMPLEX)
sin q
1
**
cos q
1
**
sin q
2
**
cos q
2
* imag{Y(n-k+1)}
* x(n-k+1) real{Y(n-k+1)}
** *
sin q
n
**
cos q
n
x(n-2) imag{Y(n-2)}
x(n-1) real{Y(n-2)}
x(n) imag{Y(n-1)}
real{Y(n-1)}
imag{Y(n)}
real{Y(n)}
K + 1 bytes M + 1 bytes N + 1 bytes
Figure 16-27. DEMOD Modulation Table and Sample Data Buffers
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
OFFSET + 0
S RES W I RES OPCODE
OFFSET + 2
I
OFFSET + 4
K
OFFSET + 6
DPTR
OFFSET + 8
M
OFFSET + A
XYPTR
OFFSET + C
N
OFFSET + E
RESERVED