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LF2301JC55

Image Resampling Sequencer

LOGIC Devices Incorporated 

DEVICES INCORPORATED

LF2301

Image Resampling Sequencer

TABLE 1. MODE SELECTION

M1 M0

MODE

0 0 single-pass operation (CW)

0 1 pass 1 of two-pass operation

1 0 single-pass operation (CCW)

1 1 pass 2 of two-pass operation

R/C — Row/Column Select

When set to 0, the LF2301 functions as

a row device. When set to 1, the

LF2301 functions as a column device.

M1-0 — Mode

This 2-bit control word defines four

modes as follows (see table 1):

The 1st and 3rd modes are single-

pass operations where the device

walks through a (K + 1) x (K + 1)

kernel for each output pixel. K is the

kernel size determined by K3-0 in

Parameter Register 7. In mode 00, the

spiral walk is in the clockwise direc-

tion. In mode 10, the spiral walk is in

the counter clockwise direction.

The 2nd and 4th modes are used

together to perform a two-pass

operation. The first pass (mode 01)

performs a (K+1) kernel in the

horizontal dimension. The second

pass (mode 11) performs a (K+1)

kernel in the vertical dimension.

The result of pass 1 is stored in the

destination image memory and is used

as the source image data for the second

pass. A system to switch source and

destination memory banks could be

designed, or utilization of a second

LF2301 pair in a pipelined architecture

could be used. In this case, the system

would require a third image buffer for

the final destination image.

K3-0 — Kernel

Kernel determines the length of the

spiral walk when performing image

transformations and the size of the

filter when implementing static filters

(see table 2). When performing image

transformations, the longest spiral walk

possible is 4 x 4 pixels (Kernel = 3). For

static filters, kernels of up to 16 x 16

pixels (Kernel = 15) are possible.

FOV — Field of View

FOV determines the distance between

pixels in a spiral walk. An FOV of 1

means each step in a spiral walk is one

pixel. An FOV of 2 means each step is

two pixels, and so on. FOV can be set

as high as 7 (see Table 3). It is impor-

tant to note when FOV is 0, the x and

y addresses will not change during a

spiral walk. They will remain fixed at

the first pixel address of the spiral

walk.

ALR — Autoload

When set HIGH and upon INIT being

strobed, the LDR control is automatically

asserted which causes the data

currently stored in the Preload Registers

to be loaded into the Transformation

Parameter Registers.

AIN — Autoinit

A new transform automatically begins

if the AIN bit is HIGH when the end of

an image is reached. The DONE flag

will go HIGH for one clock cycle. If

AIN is LOW, UWRI and the DONE flag

remain HIGH until the user strobes the

INIT control to begin a new image

transformation.

PIPE — Pipe Control

In order to compensate for buffered

source image RAM, PIPE adjusts the

timing of UWRI and ACC. If the PIPE

bit is HIGH, UWRI and ACC will have

a one clock cycle delay added relative

to the generation of the target address.

TM — Test Mode

Calculations of the source image and

coefficient addresses are made by an

internal 28-bit accumulator. TM

allows access to the sign bit and the

seven bits below the four coefficient

address bits in the accumulator. When

TM is HIGH the sign bit and 11 bits

below the source image address are fed

to X11-0 (see Figure 2). When TM is

LOW, the source image address is fed

to X11-0. Two clock cycles are required

to access both the MS and LS words of

the internal accumulator.

Functional Description

The LF2301 is an address generator

designed to be used in an image

transformation system (ITS). When

implementing an LF2301-based ITS,

second-order image transformations

can be performed like resampling,

rotation, warping, panning, and

rescaling, all at real-time video rates.

2D filtering operations, like pixel

convolutions, can also be performed.

In most applications two LF2301s are

used, one to generate the row addresses

and the other to generate the column

TABLE 2. KERNEL

K3 K2 K1 K0

00 00

00 01

00 10

00 11

01 00

01 01

01 10

01 11

10 00

10 01

10 10

10 11

11 00

11 01

11 10

11 11

Kernel

1x1

2x2

3x3

4x4

5x5

6x6

7x7

8x8

9x9

10 x 10

11 x 11

12 x 12

13 x 13

14 x 14

15 x 15

16 x 16

TABLE 3. FIELD OF VIEW

F2 F1 F0

FOV

0

0

0

0

0

0

1

1

0

1

0

2

0

1

1

3

1

0

0

4

1

0

1

5

1

1

0

6

1

1

1

7

Video Imaging Products

2-4

08/16/2000–LDS.2301-H

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