PDSP16488AMA datasheet(8/30 Pages) MITEL

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PDSP16488A MA

DELAY COMPENSATION FOR LARGE WINDOWS

A large window is composed of several partial windows

each of which is implemented in an individual device. If

necessary the partial window must be padded with zero

coefficients to become one of the standard sizes. When

constructing a large window it is necessary to delay the

expansion data inputs in order to compensate for growth in the

horizontal direction.

Delays in the partial sums are also

necessary to compensate for the total pipeline delay needed

to produce the previous complete horizontal stripe.

Within each device in a horizontal stripe, apart from

the first, the expansion input must be delayed by the width of

the partial window, before it is added to the internal sum. Since

partial windows can only be 4 or 8 pixels wide,a delay of 4 or

8 pixel clocks is needed. There is, however, an in-built delay

Fig. 6. Multi-Device Delay Paths

delays

line

delays

4 clock

delay

4 clock

delay

delays

B3 = 1

D3:2 = 00

D0 = 0

0/4

delays

line

delays

4 clock

delay

delays

B3 = 1

D3:2 = 00

D0 = 0 or 1

ZERO

WIDTH = S

0 IF S = 4, 4 IF S = 8

WIDTH = S

N th DEVICE IN THE ROW

INPUT

0/4

delays

line

delays

4 clock

delay

delays

B3 = 0

delays

line

delays

4 clock

delay

4 clock

delay

delays

B3 = 0

D0 = 0

D = 4+S(N-1) Defined by D3:2

WIDTH = S

0 IF S = 4, 4 IF S = 8

WIDTH = S

N th DEVICE IN THE ROW

0/4

delays

line

delays

4 clock

delay

delays

B3 = 0

D0 = 0 OR 1

delays

line

delays

4 clock

delay

delays

B3 = 0

D0 = 0

WIDTH = S

0 IF S = 4,4 IF S = 8

WIDTH = S

N th DEVICE IN THE ROW

OUTPUT

D = 4+S(N-1) Defined by D3:2

D0 = 0 OR 1

of 4 pixels in the inter device connection, and the

PDSP16488A thus only needs an

option

to delay the

expansion input by an additional four pixels.

The data from the last device in a horizontal row of

convolvers feeds the expansion input of the first device in the

next row. This is shown in Figure 6. With this arrangement, the

position of the partial window as illustrated, is the inverse of

its vertical position on a normal TV screen. Thus the top, left

hand, device corresponds to the bottom, left hand, portion of

the complete window.

The output from the last device in the row is delayed

with respect to the original data input by an amount given by

the formula;

DELAY = 4 + [N-1].S where N is the number of devices in

a row and S is the partial window width, ie 4 or 8.

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