
Parameter Name Type Required Description
COEF1_[] Integer No Specifies the coefficient value
[0..7] for the inputs of the
second multiplier. The
number of coefficient bits
must be set similar to the
value of WIDTH_COEF.
COEF2_[] Integer No Specifies the coefficient value
[0..7] for the inputs of the
third multiplier. The number
of coefficient bits must be set
similar to the value of WIDTH_
COEF.
COEF3_[] Integer No Specifies the coefficient value
[0..7] for the inputs of the
fourth multiplier. The
number of coefficient bits
must be set similar to the
value of WIDTH_COEF.
Design Example: Shift Accumulator
A multiplier-accumulator can be used to implement FIR filters. This design example uses the
ALTMULT_ACCUM megafunction to implement a serial FIR filter, in which both the data and
coefficient are shifted serially into the multiplier and then summed in the accumulator. This example uses
the MegaWizard Plug-In Manager in the Quartus II software.
The following design files can be found in altmult_accum_DesignExample.zip:
serial_fir.qar (archived Quartus II design files)
altmult_accum_ex_msim (ModelSim-Altera files)
Understanding the Simulation Results
The following settings are observed in this example:
• The dataa[] and datab[] input widths are both set to 16 bits
• The output port, result[] is set to a width of 33 bits
• The accum_sload input is enabled
The following figure shows the expected simulation results in the ModelSim-Altera software.
UG-01063
2014.12.19
Design Example: Shift Accumulator
8-19
ALTMULT_ACCUM (Multiply-Accumulate)
Altera Corporation
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