lf3321qc9 LOGIC Devices Incorporated, lf3321qc9 Datasheet - Page 5

• Manufacturer Part Number: lf3321qc9
• Description: Horizontal Digital Image Filter
• Manufacturer: LOGIC Devices Incorporated

DEVICES INCORPORATED
Data Reversal
LOGIC Devices Incorporated
When interleaved data is fed through the device and an even tap filter is desired, the filter should be
configured for an even number of taps and the I/D Register length should match the number of data sets
interleaved together. When interleaved data is fed through the device and an odd tap filter is desired, the
filter should be set to Odd-Tap Interleave Mode. Bit 0 of Configuration Register 1 and Configuration Register
3 configures Filters A and B respectively for Odd-Tap Interleave Mode. When the filter is configured for
Odd-Tap Interleave Mode, data from the next to last I/D Register in the forward data path is fed into the
first I/D Register in the reverse data path.
When the filter is configured for an odd number of taps (interleaved or non-interleaved modes), the filter is
structured such that the center data value is aligned simultaneously at the A and B inputs of the last ALU in
the forward data path. In order to achieve the correct result, the user must divide the coefficient by two.
Data reversal circuitry is placed after the multiplexers which route data from the forward data path to the
reverse data path (see Figure 6). When decimating, the data stream must be reversed in order for data to
be properly aligned at the inputs of the ALUs.
Functional Description
Figure 5. I/D Register Data Paths
Figure 6. Data Reversal
EVEN-TAP MODE
A
ALU
B
A
ALU
B
COEF 7
COEF 6
5
A
ODD-TAP MODE
ALU
B
A
ALU
B
Delay Stage N 1
Delay Stage N
COEF 7
COEF 6
2
Horizontal Digital Image Filter
Improved Performance
ODD-TAP INTERLEAVE MODE
Video Imaging Products
A
ALU
B
Feb 5, 2003 LDS.3321-A
A
ALU
B
LF3321
COEF 7
COEF 6
2