Nco ip core functional description, Nco ip core functional description -1 – Altera NCO MegaCore Function User Manual
Page 18
NCO IP Core Functional Description
3
2014.12.15
UG-NCO
Figure 3-1: NCO Block Diagram
sine
cosine
f
INC
f
FM
Internal
Dither
f
DITH
Waveform
Generation
Unit
Phase Accumulator
Phase
Increment
Frequency
Modulation
Input
f
PM
Phase
Modulation
Input
Dither
Generator
D
Required
Optional
The NCO IP core allows you to generate a variety of NCO architectures. Your custom NCO includes both
time- and frequency-domain analysis tools. The custom NCO outputs a sinusoidal waveform in two's
complement representation.
The waveform for the generated sine wave is defined by the following equation:
s(nT) = A sin[2π(f
O
+ f
FM
)nT + ϕ
PM
+ ϕ
DITH
)]
where:
• T is the operating clock period
• f
O
is the unmodulated output frequency based on the input value ϕ
INC
• f
FM
is a frequency modulating parameter based on the input value ϕ
FM
• ϕ
PM
is derived from the phase modulation input value P and the number of bits (P
width
) used for this
value by the equation: ϕ
PM
= P/2^P
width
• ϕ
DITH
is the internal dithering value
• A is 2
N
-1 where N is the magnitude precision (and N is an integer in the range 10 to 32
The generated output frequency, f
o
for a given phase increment, ϕ
inc
is determined by the equation: f
0
=
ϕ
inc
f
clk
/2M Hz
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