hsp43168 Intersil Corporation, hsp43168 Datasheet - Page 13

• Manufacturer Part Number: hsp43168
• Description: Dual Fir Filter
• Manufacturer: Intersil Corporation

In the Data Flow Diagrams of Figure 10, the order of the data
samples input in to the filter cell is shown by the numbers in
the forward and backward shifting decimation paths. The
output of the filter cell is given by the equation at the bottom
of the block. The diagram in Figure 10A shows data sample
alignment at the pre-adders for the Data/Coefficient
Alignment shown in Figure 9.
This dual filter application is configured by writing 110H to
Address 000H via the microprocessor interface, CIN0-9, A0-8,
and WR. Also, data reversal must be disabled by setting bit 4
of the Control Register at Address 0001H. As in the 8-tap
example, only the unique coefficients need to be stored in the
Coefficient Bank. These coefficients are stored in the first
coefficient set for FIR A by writing C0, C1, C2, and C3 to
Address 100H, 101H, 102H, and 103H respectively. To write
the same filter to the first coefficient set for FIR B, the address
sequence would change to 104H, 105H, 106H, and 107H.
The control signals TXFR, FWRD, RVRS, ACCEN, SHFTEN,
and CSEL0-4 are controlled as described in Example 1.
Example 3. Asymmetric Filter Example
The FIR cells within the HSP43168 can each calculate 4
asymmetric taps on each clock. Thus, a single FIR cell can
implement an 8-tap asymmetric filter if the HSP43168 is
clocked at twice the input data rate. Similarly, if the Dual is
configured as a single filter, a 16-tap asymmetric filter is
realizable. Only one of the two FIR cells are used in this
example for the Block Diagram shown in Figure 11.
For this example, the FIR cells are configured as two 8-tap
asymmetric filters which are clocked at twice the input data
rate. New data is shifted into the forward and backward
decimation paths every other CLK by the assertion of
SHFTEN. The filter output is computed by passing data from
each decimation path to the multipliers on alternating clocks.
Two sets of coefficients are required, one for data on the
forward decimation path, and one for data on the reverse
path. The filter output is generated by accumulating the
multiplier outputs for two CLKs.
FIGURE 10C. DATA FLOW AS DATA SAMPLE 8 IS CLOCKED
FIGURE 10. DATA FLOW DIAGRAMS FOR 7-TAP SYMMETRIC
C0
8
(X8+X2)C0+(X7+X3)C1+(X6+X4)C2+(X5+X5)C3/2
+
FILTER
INTO THE FEED FORWARD STAGE
C1
2
7
+
C2
3
6
+
13
+
C3/2
4
5
+
5
HSP43168
The operation of this configuration is better understood by
comparing the Data/Coefficient Alignment in Figure 12 with
the Data Flow Diagrams in Figure 13. The ALUs have been
omitted from the FIR cell diagrams because data is fed to the
multipliers directly from the forward and reverse decimation
paths. The data samples within the FIR cell are shown by the
numbers in the decimation paths.
FIGURE 12. DATA/COEFFICIENT ALIGNMENT FOR 8-TAP
FIGURE 11. USING HSP43168 AS TWO INDEPENDENT
INA0-9
INB0-9
h(n)
x(n)
A
B
A
B
X9
FILTERS
ASYMMETRIC FILTER
X8
8-TAP ASYMMETRIC
8-TAP ASYMMETRIC
C7
X7
FIR A
FIR B
C6
X6
HSP43168
C5
X5
C4
X4
M
U
X
C3
X3
C2
X2
C1
X1
8-TAPS
OUT9-27
C0
X0