AD9929BBCZ datasheet(46/64 Pages) AD

46 / 64 page

AD9929

Rev. A | Page 46 of 64

TIMING CONTROL

ELECTRONIC SHUTTER TIMING CONTROL

CCD image exposure time is controlled through the use of the

CCD substrate clock signal (XSUBCK), which pulses the CCD

substrate to clear out accumulated charges prior to the exposure

period. The AD9929 supports three types of electronic shut-

tering: normal shutter mode, suppression shutter mode, and

high speed shutter mode. Table 34 contains the registers

required for programming of XSUBCK pulses for each mode.

Normal Shutter Mode

Figure 49 shows the VD and XSUBCK output for normal

shutter mode. The XSUBCK pulses once per line. The number

of XSUBCK pulses per field can be programmed by setting

the XSUBCK pulses always begin on the line after the sensor

gate, as specified by XVSGACTLINE (Mode_Reg(1)).

SUBCK Suppression Mode

Normally, the XSUBCKs begin to pulse on the line following

the last sensor gate line (VSG). With some CCDs, the first

XSUBCK following the VSG line needs to be suppressed. The

XSUBCKSUPPRESS register allows for this suppression. The

first XSUBCK following the last VSG pulse is suppressed when

XSUBCKSUPPRESS = 1, as shown in Figure 50.

High Precision Shutter Mode

The high speed shutter mode can be operated in two different

modes, known as single pulse mode and multiple pulse mode.

These modes are set up by programming the

XSUBCKNUM_HP register and XSUBCKMODE_HP register,

as described in Table 28, Table 33, and shown in Figure 52 and

Figure 54.

Single Pulse Mode

In addition to the normal operating XSUBCK pulse, one addi-

tional XSUBCK pulse can be applied within the HD line while

operating in this mode. As shown in Figure 49, the location of

the additional XSUBCK pulse is adjustable by setting the

XSUBCK_HPNUM register as described in Table 33. Finer

resolution of the exposure time is possible using this mode by

adding an additional XSUBCK pulse in the line, as shown in

Figure 54.

Multiple Pulse Mode

In addition to the normal operating XSUBCK pulse, up to seven

sequential XSUBCK pulses can be applied within the same line

while operating in this mode. As shown in Figure 54, the num-

ber of additional XSUBCK pulses is selectable by setting

XSUBCKMODE_HP = 1, and the XSUBCK_HPNUM registers

as described in Table 33.

Table 33. Single and Multiple Pulse Mode

XSUBCKNUM_HP

XSUBCKMODE_HP

Single Pulse Mode

Multiple

Pulse Mode

Normal Shutter

Mode Operation

Normal Shutter

Mode Operation

Position #1

1 additional pulse

Position #2

2 additional pulses

Position #3

3 additional pulses

Position #4

4 additional pulses

Position #5

5 additional pulses

Position #6

6 additional pulses

Position #7

7 additional pulses

Table 34. XSUBCK Registers

Bit

Width

Reference

Counter

Range

Description

XSUBCKNUM

Control (Address 0x0B)

–

0–2047 Number of

Pulses

Number of XSUBCK Pulses per Field.

XSUBCKSUPPRESS

Control (Address 0x01)

–

0–1 Number of Pulses

Suppress First XSUBCK after Last XVSG

Line Pulse

XSUBCK_EN

Control (Address 0x0B)

–

XSUBCK Output Enable Control

(0 = Disable, 1 = Enable)

XSUBCKMODE_HP

Control (Address 0x01)

–

High Speed Shutter Mode Operation

XSUBCKNUM_HP

Control (Address 0x0B)

–

0–7 Number of Pulses

High Speed Shutter XSUBCLK

Position/Number

XSUBCK1TOG1

System_Reg(14)

OL Counter

0–511 Pixel Location

XSUBCLK1 1st Toggle Position

XSUBCK1TOG2

System_Reg(14)

OL Counter

0–511 Pixel Location

XSUBCLK1 2nd Toggle Position

XSUBCK2TOG1

System_Reg(15)

OL Counter

0–511 Pixel Location

XSUBCLK2 1st Toggle Position

XSUBCK2TOG2

System_Reg(15)

OL Counter

0–511 Pixel Location

XSUBCLK2 2nd Toggle Position

XSUBCKSEL

Mode_Reg(2)

–

(0 = XSUBCK1, 1 = XSUBCK2)

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