AD9942BBCZ datasheet(24/36 Pages) AD

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AD9942

Rev. A | Page 24 of 36

CHANNEL A AND CHANNEL B SPECIAL HBLK PATTERNS

Six toggle positions are available for HBLK. Typically, only two

of the toggle positions are used to generate the standard HBLK

interval. However, the additional toggle positions can be used to

generate special HBLK patterns, as shown in Figure 24. The

pattern in this example uses all six toggle positions to generate

two extra groups of pulses during the HBLK interval. By

changing the toggle positions, different patterns can be created.

HORIZONTAL SEQUENCE CONTROL

The AD9942 uses sequence change positions (SCPs) and

sequence pointers (SPTRs) to organize the individual horizontal

sequences. Up to four SCPs are available to divide the readout

into four separate regions, as shown in Figure 25. The SCP0 is

always hard-coded to Line 0, and SCP1 to SCP3 are register

programmable. During each region bounded by the SCP, the

SPTR registers designate which sequence is used by each signal.

CLPOB, PBLK, and HBLK each have a separate set of SCPs. For

example, CLPOBSCP1 defines Region 0 for CLPOB, and in that

region any of the four CLPOB sequences can be selected with

the CLPOBSPTR register. The next SCP defines a new region,

in which each signal can be assigned to a different individual se-

quence. The sequence control registers are detailed in Table 21.

HBLK

SPECIAL H-BLANK PATTERN IS CREATED USING MULTIPLE HBLK TOGGLE POSITIONS.

H1X/H3X

H2X/H4X

TOG1

TOG2

TOG3

TOG4

TOG5

TOG6

Figure 24. Generating Special HBLK Patterns

UP TO FOUR INDIVIDUAL HORIZONTAL CLAMP AND BLANKING REGIONS MAY BE

PROGRAMMED WITHIN A SINGLE FIELD, USING THE SEQUENCE CHANGE POSITIONS.

SEQUENCE CHANGE OF POSITION 1

SEQUENCE CHANGE OF POSITION 2

SEQUENCE CHANGE OF POSITION 3

SINGLE FIELD (1 VD INTERVAL)

CLAMP AND PBLK SEQUENCE REGION 0

SEQUENCE CHANGE OF POSITION 0

(V COUNTER = 0)

CLAMP AND PBLK SEQUENCE REGION 3

CLAMP AND PBLK SEQUENCE REGION 2

CLAMP AND PBLK SEQUENCE REGION 1

Figure 25. CLPOB and PBLK Sequence Flexibility

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