LF3338 Datasheet, PDF (5/15 Pages) LOGIC Devices Incorporated – 8-Bit Vertical Digital Image Filter

DEVICES INCORPORATED
LF3338
8-Bit Vertical Digital Image Filter
FUNCTIONAL DESCRIPTION
Line Buffers
The maximum delay length of each line
buffer is 3076 cycles and the minimum
is 4 cycles. Configuration Register 0
(CR0) determines the delay length of
the line buffers. The line buffer length
is equal to the value of CR0 plus 4. A
value of 0 for CR0 sets the line buffer
length to 4. A value of 3072 for CR0
sets the line buffer length to 3076. Any
values for CR0 greater than 3072 are not
valid.
The line buffers have two modes of
operation: delay mode and recirculate
mode. Bit 0 of Configuration Register 1
determines which mode the line buffers
are in. In delay mode, the data input to
the line buffer is delayed by an amount
determined by CR0. In recirculate
mode, the output of the line buffer is
routed back to the input of the line
buffer allowing the line buffer contents
to be read multiple times.
Bit 1 of Configuration Register 1 allows
the line buffers to be loaded in parallel.
When Bit 1 is “1”, the input register
(DIN7-0) loads all seven line buffers in
parallel. This allows all the line buffers
to be preloaded with data in the
amount of time it normally takes to
load a single line buffer.
Odd and Even Field Filtering
The LF3338 is capable of odd and even
field filtering. Bit 2 of Configuration
Register 1 enables the VB Data Input
port required for odd and even field
filtering. Bit 3 of the same configura-
tion register enables the line buffer in
the VB Data path. Line buffer length is
set to the length written to Configura-
tion Register 0. If line buffer parallel
load is enabled and odd and even field
filtering is enabled, the data for the VB
line buffer comes from the VB Data
Input port.
Interleaved Data
The LF3338 is capable of handling
interleaved data. The number of data
sets it can handle is determined by the
number of data values contained in a
video line. If the interleaved video line
has 3076 data values or less, the LF3338
can handle it no matter how many data
sets are interleaved together.
Cascading
A cascade port is provided to allow
cascading of multiple devices for
more filter taps (see Figure 5).
COUT7-0 of one device should be
connected to DIN7-0 of another
device. As many LF3338s as desired
may be cascaded together. How-
ever, the outputs of the LF3338s
must be added together with exter-
nal adders.
The first line buffer on a cascaded
device must have its length short-
ened by two delays. This is to
account for the added delays of the
input register on the device and the
cascade output register from the
previous LF3338. If Bit 0 of Con-
figuration Register 3 is set to “1”,
the length of the first line buffer will
be reduced by two. This will make
its effective length the same as the
other line buffers on the device. If
Bit 0 of Configuration Register 3 is
set to “0”, the length of the first line
buffer will be the same as the other
line buffers. When cascading
devices, the first LF3338 should
have Bit 0 of Configuration Register
FIGURE 5.
8
DIN
MULTIPLE LF3338S CASCADED TOGETHER
LF3338
LF3338
LINE BUFFERS
COUT
DIN
LINE BUFFERS
COUT
DIN
LF3338
LINE BUFFERS
COUT
DIN
LF3338
LINE BUFFERS
VERTICAL FILTER
RSL
CIRCUIT
VERTICAL FILTER
RSL
CIRCUIT
VERTICAL FILTER
RSL
CIRCUIT
VERTICAL FILTER
RSL
CIRCUIT
LF3347
25
25
RSL
CIRCUIT
16
DATA OUT
29 TAP RESULT
5
Video Imaging Products
04/06/1999–LDS.3338-B