LF2272QC20 데이터 시트보기 (PDF) - LOGIC Devices

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LF2272QC20

Colorspace Converter/Corrector (3 x 12-bits)

LOGIC Devices 

DEVICES INCORPORATED

LF2272

Colorspace Converter/

Corrector (3 x 12-bits)

products will be output five clock

cycles after the input data has been

registered. New output data is

subsequently available every clock

cycle thereafter.

TABLE 1. LATENCY EQUATIONS

X(n+4) = A(n)KA1(n) + B(n)KB1(n) + C(n)KC1(n)

Y(n+4) = A(n)KA2(n) + B(n)KB2(n) + C(n)KC2(n)

DATA FORMATTING

Z(n+4) = A(n)KA3(n) + B(n)KB3(n) + C(n)KC3(n)

The data input ports (A, B, C) and

data output ports (X, Y, Z) are 12-bit

integer two’s complement format.

DATA OVERFLOW

SYSTEMS SMALLER THAN 12-BITS

The coefficient input ports (KA, KB,

KC) are 10-bit fractional two’s

complement format. Refer to

Figures 1a and 1b.

BIT WEIGHTING

The internal sum of products of the

LF2272 can grow to 23 bits. However,

in order to keep the output format

identical to the input format, the X, Y,

and Z outputs are rounded to 12-bit

integer words. The rounding is done

only at the final output stage to allow

accuracy, with correct rounding and

overflow, for applications requiring

less than 12-bit integer words. The

user may adjust the bit weighting by

applying an identical scaling correc-

tion factor to both the input and

output data streams.

Because the LF2272’s matched input

and output data formats accommo-

date unity gain (0 dB), input condi-

tions that could lead to numeric

overflow may exist. To ensure that no

overflow conditions occur, the user

must be aware of the maximum input

data and coefficient word sizes

allowable for each specific algorithm

being performed.

Using a data path less than 12-bits

requires the input data to be right

justified and sign extended to 12-bits

because the LF2272 carries out all

calculations to full precision. Since all

least-significant bits are used, the

desired X, Y, and Z outputs are

rounded correctly and upper-order

output bits are used for overflow.

FIGURE 1A. INPUT FORMATS

Data Input

11 10 9 8 7 6 5 4 3 2 1 0

–211 210 29 28 27 26 25 24 23 22 21 20

(Sign)

Coefficient Input

98765 43210

–20 2–1 2–2 2–3 2–4 2–5 2–6 2–7 2–8 2–9

(Sign)

Internal Sum

20 19 18 17

–211 210 29 28

(Sign)

3210

2–6 2–7 2–8 2–9

FIGURE 1B. OUTPUT FORMAT

Result

11 10 9 8 7 6 5 4 3 2 1 0

–211 210 29 28 27 26 25 24 23 22 21 20

(Sign)

Video Imaging Products

2

08/16/2000–LDS.2272-I

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