Motorola MPC823e Reference Manual page 481

16.3.2.1 HARDWARE. The RISC microcontroller's hardware contains special DSP
processing units, such as a multiplier and accumulator that is capable of handling real or
complex numbers, and an address generator that can access cyclic buffer structures in
dual-port RAM.
16.3.2.2 SOFTWARE. Your software interfaces to the DSP via the function descriptor that
is described in system memory. The function descriptor defines the sequence and data flow
of your DSP task.
16.3.2.3 FIRMWARE. The RISC microcontroller's firmware is a set of DSP functions that
have been compiled to form a library of basic building blocks and each function within the
library is implemented by a microcode routine stored in the internal ROM. In addition, a
software interface is defined that enables parameters to be passed between the core and
communication processor module. Several functions can be chained together to reduce
software intervention and interrupt rates, assuming that all data structures reside in the
dual-port RAM. Table 16-6 lists the DSP functions that are included in the library.
FUNCTION OPCODE
FIR1 00001
FIR2 00010
FIR3 00011
FIR5 00011
FIR6 00110
IIR 00111
MOD 01000
DEMOD 01001
LMS1 01010
LMS2 01011
WADD 01100
16.3.3 Programming the DSP Functions
Similar to the serial communication controller buffer descriptor, a function descriptor (FD) is
used to specify the DSP function and pass the parameters. A table of such descriptors forms
a circular queue with a programmable length. The descriptors are stored in external
memory. There are two function descriptor tables (also referred to as chains)—one for the
transmitter and one for the receiver. The core prepares a chain of function descriptors in the
system memory and a special host command notifies the RISC microcontroller when to
execute the chain. A maskable interrupt is generated once the chain is completed. As
illustrated in Figure 16-8, the pointer to the transmit (TX) chain must be written into the
FDBASE field of the DSP2 parameter RAM and the pointer to the receive (RX) chain must
be written into DSP1.
MOTOROLA
Table 16-6. DSP Functions
INPUT COEFFICIENT
Real Real
Complex Real
Complex Complex
Complex Complex
Real Complex
Real Real
Complex Complex
Real Complex
— —
— —
Real —
MPC823e REFERENCE MANUAL
Communication Processor Module
OUTPUT
Real Decimation, RX Interpolation
Complex TX Filter, RX Filter
Real/Complex EC Computation, Equalizer
Real/Complex Fractionally Spaced Equalizer
Complex
Real
Real/Complex
Complex RX Demodulation
— EC Update, Equalizer Update (T/2, T/3)
— Equalizer Update (2T/3)
Real
APPLICATION
—
Biquad Filter
TX Modulation
Interpolation
16-27