CORR-8BIT-PM-U2 Lattice, CORR-8BIT-PM-U2 Datasheet - Page 2

• Manufacturer Part Number: CORR-8BIT-PM-U2
• Description: Development Software Correlator IP Core User Config
• Manufacturer: Lattice

Specifications of CORR-8BIT-PM-U2

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Lattice Semiconductor
General Description
A correlation function determines how closely a data sequence matches a reference, or “coefficient” sequence. A
high correlation value means that the data sequence closely matches the coefficient sequence. A low correlation
value means that the data sequence is dissimilar to the coefficient sequence. The basic correlator equation is given
by:
The terms of the equation are:
• d
• c
• r
• corr_win – Correlation window. This is the number of elements in the input data sequence over which the corre-
• num_lags – Total number of lags for which the correlation is performed. This is also the length of the correlation
From Equation 1, a correlation operation takes an input data sequence d
term in the sequence against the terms of the reference coefficient sequence c
multiplications to produce the result r
repeated to produce the next term in the r
In the Correlator IP core, each time a new data term is input to the core, one correlation operation is performed
across “corr_win” data and coefficient terms, producing one result, r. The “k” index in Equation 1 does not apply
since the Correlator always produces one new result when it receives one new data value. Old data beyond the
defined correlation window size is not held in memory.
In addition to the basic correlation function described above, the Correlator IP core can be configured to perform
complex correlations, defined by the equation:
In this case, the data and coefficient input sequences are both complex and each contains a real input sequence
and an imaginary input sequence. For the Correlator IP core, the input data sequence is a sequence of signed
(two’s complement) numbers from 1 to 8 bits wide, and the coefficient sequence is a binary sequence where a
coefficient value of 1 represents +1 and a coefficient value of 0 represents a -1. Equation 2 represents the complex
conjugate of c
signed (two’s complement) or unsigned data.
prior to a correlation operation. This sequence is always binary {1,0}; however, the coefficient sequence may rep-
resent either an unsigned sequence {1,0} or a signed sequence {+1,-1}. In the case of a signed coefficient
sequence, a 1 in the sequence represents a value of +1 and a 0 in the sequence represents a value of -1. The d
and c
lation function is calculated. This is also referred to as the number of “taps.” For the Correlator IP core this num-
ber is determined by the user when configuring the core. Once selected, the number of data elements (and
coefficient terms) is then fixed at this number for all correlation operations. The number of terms in the coefficient
sequence is always equal to the number of taps (corr_win) specified.
result sequence, r
k
i
i
– Coefficient (or code) sequence. In the Correlator IP core, this sequence must be loaded into internal memory
– Input data sequence. The Correlator IP core allows the input sequence to be from 1 to 8 bits wide, and either
– Correlation result output sequence (correlation between d
i
inputs must both be of the same type, either signed or unsigned.
i
. The complex conjugate multiplication expressed in Equation 2 is given as:
k.
r
r
dc = (d
k
k
k
. The input data sequence is then shifted by one element and the operation is
=
=
corr
corr
k
re
i
i
_
sequence. This is done “num_lags” times.
_
=
=
win
win
0
0
c
d
re
d
1
i
i
1
+
+
+ d
k
k
c
c
im
i
i
c
im
k = 0,1,…,num_lags-1
k = 0,1,…,num_lags-1
2
) + j(d
im
i
and c
c
re
- d
i
re
inputs).
i
c
of length “corr_win” and multiplies each
im
)
i
, summing the results of all of the
Correlator IP Core
(1)
(2)
(3)
i