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REV. 0

AD9848/AD9849

–22–

HORIZONTAL CLAMPING AND BLANKING

The AD9848/AD9849’s horizontal clamping and blanking

pulses are fully programmable to suit a variety of applications.

As with the vertical timing generation, individual sequences are

defined for each signal, which are then organized into multiple

regions during image readout. This allows the dark pixel clamp-

ing and blanking patterns to be changed at each stage of the

readout, in order to accommodate different image transfer tim-

ing and high-speed line shifts.

Individual CLPOB, CLPDM, and PBLK Sequences

The AFE horizontal timing consists of CLPOB, CLPDM, and

PBLK, as shown in Figure 9. These three signals are indepen-

dently programmed using the registers in Table IV. SPOL is the

start polarity for the signal, and TOG1 and TOG2 are the first

and second toggle positions of the pulse. All three signals are

active low, and should be programmed accordingly. Up to four

individual sequences can be created for each signal.

Individual HBLK Sequences

The HBLK programmable timing shown in Figure 10 is similar

to CLPOB, CLPDM, PBLK. However, there is not start polar-

ity control. Only the toggle positions are used, to designate the

start and the stop positions of the blanking period. Additionally,

there is a polarity control HBLKMASK which designates the

polarity of the horizontal clock signals H1 – H4 during the blank-

ing period. Setting HBLKMASK high will set H1 = H3 = low

and H2 = H4 = high during the blanking, as shown in Figure

11. Up to four individual sequences are available for HBLK.

(3)

(2)

(1)

CLPOB

CLPDM

PBLK

. . .

NOTES

PROGRAMMABLE SETTINGS:

(1) START POLARITY (CLAMP AND BLANK REGION ARE ACTIVE LOW)

(2) FIRST TOGGLE POSITION

(3) SECOND TOGGLE POSITION

CLAMP

Figure 9. Clamp and Preblank Pulse Placement

(2)

(1)

HBLK

. . .

NOTES

PROGRAMMABLE SETTINGS:

(1) FIRST TOGGLE POSITION = START OF BLANKING

(2) SECOND TOGGLE POSITION = END OF BLANKING

BLANK

Figure 10. Horizontal Blanking (HBLK) Pulse Placement

Table IV. CLPOB, CLPDM, PBLK Individual Sequence Parameters

Length

Range

Description

SPOL

High/Low

Starting Polarity of Clamp and Blanking Pulses for Sequences 0–3

TOG1

12b

0–4095 Pixel Location

First Toggle Position within the Line for Sequences 0–3

TOG2

12b

0–4095 Pixel Location

Second Toggle Position within the Line for Sequences 0–3

Table V. HBLK Individual Sequence Parameters

Length

Range

Description

HBLKMASK

High/Low

Masking Polarity for H1 for Sequences 0–3 (0 = H1 Low, 1 = H1 High)

HBLKTOG1

12b

0–4095 Pixel Location

First Toggle Position within the Line for Sequences 0–3

HBLKTOG2

12b

0–4095 Pixel Location

Second Toggle Position within the Line for Sequences 0–3

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