Fcop Memory Banks; Multiplier And Accumulator (Fmac); Programming Model - Motorola DSP56305 User Manual

Filter Co-Processor

Programming Model

12.3.2

FCOP Memory Banks

The FCOP contains two memory banks: the FCOP Data Memory bank (FDM) and the
FCOP Coefficients Memory bank (FCM).
• FCOP Data Memory bank (FDM):
84-word 16-bit wide memory, used to store data samples for filter processing by
the FCOP. It is written via a 4-word FIFO (FDIR) and its addressing is generated
by the FCOP Address Generation logic. The data samples are sequentially read
from FDM into the MAC for filter processing. The FDM can be written by both the
core and DMA.
• FCOP Coefficients Memory Bank (FCM):
42-word 16-bit wide memory, used to store filter coefficients for filter processing
by the FCOP. It is written via an input buffer (FCIR) and its addressing is
generated by the FCOP Address Generation logic. The filter samples are
sequentially read from FDM into the MAC for filter processing. The FCM can
only be written by the core.
12.3.3

Multiplier and Accumulator (FMAC)

The FCOP Multiplier and Accumulator (FMAC) machine is capable of performing a
16-bit × 16-bit multiplication with accumulation in a 40-bit accumulator. The FMAC
operates in a pipeline fashion, with the multiplication performed in one clock cycle and
the accumulation in the following clock cycle. The throughput is one MAC result per
clock cycle. The two MAC operands are read from the FDM and the FCM. The full 40-bit
width of the accumulator is used for intermediate results during the filter calculations.
After all the filter taps have been processed, the result is rounded to the nearest even and
limited to the greatest (most positive) number ($7FFF) if overflow occurred or to the least
(most negative) number ($8000) if underflow occurred. The rounding and limiting
operations take two additional clock cycles after the filter processing is completed. The
16-bit result from FMAC is stored in the FDOR to be read by the DSP56300 core.
12.4 PROGRAMMING MODEL
The programming model discusses the FCOP registers available to the programmer, and
interrupts and DMA access.
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