LF2242 datasheet(3/8 Pages) LODEV

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DEVICES INCORPORATED

LF2242

12/16-bit Half-Band Interpolating/

Decimating Digital Filter

Video Imaging Products

08/16/2000–LDS.2242-K

RND2-0 — Rounding Control

The rounding control inputs set the posi-

tionoftheeffectiveLSBoftheoutputdata

by adding a rounding bit to the internal

bit position that is one below that speci-

fied by RND2-0. 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 SO15-0 pins. When OE is HIGH, the

outputs are in a high-impedance state.

FIGURE 2.

INPUT AND OUTPUT FORMATS

RND2-0

SO15

SO14

SO13

SO12

• • •

SO8

SO7

SO6

SO5

SO4

SO3

SO2

SO1

SO0

000

• • •

XXX

XXXX

001

• • •

XXX

010

• • •

XXX

011

• • •

XXX

100

• • •

XXX

101

• • •

000

110

• • •

0000

111

• • •

0000

'R' indicates the half-LSB rounded bit (effective LSB position)

TABLE 2.

ROUNDING FORMAT

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)

–2

0 2–1 2–2

–8

–9 2–10

–3

–11

(Sign)

14 13 12

–2

0 2–1 2–2

–12 2–13 2–14

–3

–15

(Sign)

14 13 12

–2

–1

–11 2–12 2–13

–2

–14

(Sign)

14 13 12

–1 2–2

–12 2–13 2–14

–3

–15

(Sign)

14 13 12

–1

–11 2–12 2–13

–2

–14

(Sign)

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