AD9895 データシートの表示（PDF） - Analog Devices

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AD9895

CCD Signal Processors with Precision Timing™ Generator

Analog Devices 

HORIZONTAL CLAMPING AND BLANKING

The AD9891/AD9895’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 clamping and

blanking patterns to be changed at each stage of the readout in

order to accommodate different image transfer timing 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 13. These three signals are indepen-

dently programmed using the registers in Table III. 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.

AD9891/AD9895

To simplify the programming requirements, the CLPDM signal

will track the CLPOB signal by default. If separate control of

the CLPDM signal is desired, the SINGLE_CLAMP Register

(Addr x031) should be set LOW.

Individual HBLK Sequences

The HBLK programmable timing shown in Figure 14 is similar

to CLPOB, CLPDM, and PBLK. However, there is no start

polarity control. Only the toggle positions are used to designate

the start and the stop positions of the blanking period. Addition-

ally, there is a polarity control, HBLKMASK, that 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 15.

Up to four individual sequences are available for HBLK.

Horizontal Sequence Control

The AD9891/AD9895 use sequence change positions (SCP)

and sequence pointers (SPTR) to organize the individual hori-

HD

1

CLPOB

CLPDM

PBLK

2

3

CLAMP

PROGRAMMABLE SETTINGS:

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

2: 1ST TOGGLE POSITION

3: 2ND TOGGLE POSITION

Figure 13. Clamp and Preblank Pulse Placement

CLAMP

HD

HBLK

1

2

BLANK

BLANK

PROGRAMMABLE SETTINGS:

1: 1ST TOGGLE POSITION = START OF BLANKING

2: 2ND TOGGLE POSITION = END OF BLANKING

Figure 14. Horizontal Blanking (HBLK) Pulse Placement

HD

HBLK

H1/H3

H1/H3

H2/H4

THE POLARITY OF H1 DURING BLANKING IS PROGRAMMABLE (H2 IS OPPOSITE POLARITY OF H1)

Figure 15. HBLK Masking Control

REV. A

–15–

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