lf3320 LOGIC Devices Incorporated, lf3320 Datasheet - Page 12

• Manufacturer Part Number: lf3320
• Description: Horizontal Digital Image Filter
• Manufacturer: LOGIC Devices Incorporated

DEVICES INCORPORATED
reverse data path (see Figure 14).
When decimating, the data stream
must be reversed in order for data to
be properly aligned at the inputs of
the ALUs.
When data reversal is enabled, the cir-
cuitry uses a pair of LIFOs to reverse
the order of the data sent to the
reverse data path. TXFRA and TXFRB
control the LIFOs in Filters A and B
F
F
IGURE
IGURE
DIN
12
14. D
15. M
TXFRA/TXFRB
REGISTERS
FILTER
LIFO A
LIFO B
I/D
A
ATA
ULTIPLE
LF3320
CIRCUIT
16
RSL
R
REGISTERS
EVERSAL
FILTER
I/D
B
LF3320
RIN
COUT
S
ROUT
DIN
C
ASCADED
respectively. When TXFRA/TXFRB
goes LOW, the LIFO sending data
to the reverse data path becomes the
LIFO receiving data from the forward
data path, and the LIFO receiving data
from the forward data path becomes
the LIFO sending data to the reverse
data path. The device must see a
HIGH to LOW transition of TXFRA/
TXFR B in order to switch LIFOs.
If decimating by N, TXFRA/TXFRB
should go LOW once every N clock
cycles. When data reversal is dis-
abled, the circuitry functions like an
I/D Register. When feeding inter-
leaved data through the filter, data
reversal should be disabled. Bit 6
of Configuration Register 1 and Con-
figuration Register 3 enables or dis-
ables data reversal for Filters A
and B respectively.
Cascading
Three cascade ports are provided to
allow cascading of multiple devices
for more filter taps (see Figure 15).
COUT
REGISTERS
FILTER
I/D
A
LF3320
CIRCUIT
16
11-0
RSL
T
REGISTERS
FILTER
of one device should be
OGETHER
I/D
B
128 TAP RESULT
2-12
25
RIN
COUT
LF3347
DATA OUT
CIRCUIT
16
RSL
ROUT
DIN
25
REGISTERS
FILTER
I/D
A
LF3320
CIRCUIT
16
RSL
Horizontal Digital Image Filter
REGISTERS
FILTER
I/D
B
connected to DIN
device. ROUT
should be connected to RIN
another device. As many LF3320s
as desired may be cascaded together.
However, the outputs of the LF3320s
must be added together with external
adders.
Bit 0 of Configuration Register 5 deter-
mines how the device will send data
to the reverse data path when mul-
tiple LF3320s are cascaded together.
If a LF3320 is the last in the cascade
chain, Bit 0 of Configuration Register 5
should be set to a “0”. This will cause
the data from the end of the forward
data path to be routed to the begin-
ning of the reverse data path based on
how the filter is configured (even/odd
number of taps or interleave mode). If
a LF3320 is not the last in the cascade
chain, Bit 0 of Configuration Register 5
should be set to a “1”. This will cause
Video Imaging Products
RIN
COUT
ROUT
DIN
11-0
REGISTERS
FILTER
I/D
A
11-0
LF3320
of one device
CIRCUIT
16
RSL
of another
REGISTERS
FILTER
6/22/2007–LDS.3320-R
I/D
B
11-0
LF3320
of