AD9898 datasheet(25/52 Pages) AD

25 / 52 page

REV. 0

AD9898

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HORIZONTAL CLAMPING AND BLANKING

The AD9898’s horizontal clamping and blanking pulses are

programmable to suit a variety of applications. Similar to verti-

cal timing generation, individual sequences are defined for each

signal and 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 to accommo-

date different image transfer timing and high speed line shifts.

Controlling CLPOB Clamp Pulse Timing

The AFE horizontal CLPOB pulse is generated based on the

12-bit gray code counter. Once the length of the 12-bit gray

code counter is set using the HDLEN register (Sys_Reg(12)),

CLPTOG1 and CLPTOG2 registers (Sys_Reg(15 and16)) can

be used to place the CLPOB pulse location, as shown in Figure 19.

Table XII lists all CLPOB registers that are used to configure

and control the placement and output of the CLPOB pulse.

The length of the last HD line is set using the HDLASTLEN

will be asserted when the last HD length set by HDLASTLEN

is shorter than the regular HD length set by HDLEN.

Figure 21 shows that no CLPOB pulse will be applied when the

last HD length set by HDLASTLEN is longer than the regular

HD length. Note that the CLPOB pulse is applied in the last

line only when HDLASTLEN = HDLEN.

LAST LINE

CLPOB

Figure 20. Last HD Shorter Than Regular HD

LAST LINE

CLPOB

Figure 21. Last HD Longer Than Regular HD

Table XII. CLPOB Registers

Bit

Reference

Name

Width Register Type

Counter

Range

Description

CLP_CONT 1

Control (0x01)

CLPOB Control (0 = CLPOB Off, 1 = CLPOB On)

CLP_MODE 1

Control(0x01)

CLPOB CCD Region Control

(0 = Enable CLPENx Register Settings,

1 = Disable CLPENx Register Settings)

CLPTOG1

Sys_Reg(15)

0–4095 Pixel Locations CLPOB Toggle Position 1 (Gray Code Number)

CLPTOG2

Sys_Reg(15 and 16) HD

0–4095 Pixel Locations CLPOB Toggle Position 2 (Gray Code Number)

CLPEN0

Mode_Reg(2)

CLPOB Control for CCD Region 0