
DEVICES INCORPORATED
LF2242
12/16-bit Half-Band Interpolating/
Decimating Digital Filter
Video Imaging Products
3
08/16/2000–LDS.2242-K
RND
2-0
— Rounding Control
The rounding control inputs set the posi-
tion of the effective LSB of the output data
by adding a rounding bit to the internal
bit position that is one below that speci-
fied by RND
2-0
. All bits below the effec-
tive LSB position are subsequently ze-
roed (Table 2).
TCO — Two’s Complement Format
Control
The TCO input determines the format of
the output data. When TCO is HIGH, the
output data is presented in two’s comple-
ment format. When TCO is LOW, the
data is in inverted offset binary format
(all output bits are inverted except the
MSB — the MSB is unchanged).
OE — Output Enable
When the OE signal is LOW, the current
data in the output register is available on
the SO
15-0
pins. When OE is HIGH, the
outputs are in a high-impedance state.
F
IGURE
2.
I
NPUT
AND
O
UTPUT
F
ORMATS
RND
2-0
SO
15
SO
14
SO
13
SO
12
SO
8
SO
7
SO
6
SO
5
SO
4
SO
3
SO
2
SO
1
SO
0
000
X
X
X
X
X
X
X
X
X
X
X
X
R
001
X
X
X
X
X
X
X
X
X
X
X
R
0
010
X
X
X
X
X
X
X
X
X
X
R
0
0
011
X
X
X
X
X
X
X
X
X
R
0
0
0
100
X
X
X
X
X
X
X
X
R
0
0
0
0
101
X
X
X
X
X
X
X
R
0
0
0
0
0
110
X
X
X
X
X
X
R
0
0
0
0
0
0
111
X
X
X
X
X
R
0
0
0
0
0
0
0
'R' indicates the half-LSB rounded bit (effective LSB position)
T
ABLE
2.
R
OUNDING
F
ORMAT
Two’s Complement Input Format
Two’s Complement Output Format (TCO = 1, Non-interpolate)
Two’s Complement Output Format (TCO = 1, Interpolate)
Inverted Offset Binary Output Format (TCO = 0, Non-interpolate)
Inverted Offset Binary Output Format (TCO = 0, Interpolate)
10
9
8
2
1
0
11
–2
0
2
–1
2
–2
(Sign)
3
2
–8
2
–9
2
–10
2
–3
2
–11
14 13 12
–2
0
2
–1
2
–2
(Sign)
2
1
0
15
3
2
–12
2
–13
2
–14
2
–3
2
–15
14 13 12
–2
1
2
0
2
–1
(Sign)
2
1
0
15
3
2
–11
2
–12
2
–13
2
–2
2
–14
14 13 12
2
0
2
–1
2
–2
(Sign)
2
1
0
15
3
2
–12
2
–13
2
–14
2
–3
2
–15
14 13 12
2
1
2
0
2
–1
(Sign)
2
1
0
15
3
2
–11
2
–12
2
–13
2
–2
2
–14