AD9948 datasheet(17/28 Pages) AD

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REV. 0

AD9948

–17–

HBLK

. . .

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

H1/H3

H2/H4

. . .

Figure 10. HBLK Masking Control

HBLK

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

H1/H3

H2/H4

TOG1

TOG2

TOG3

TOG4

TOG5

TOG6

Figure 11. Generating Special HBLK Patterns

GENERATING SPECIAL HBLK PATTERNS

Six toggle positions are available for HBLK. Normally, only

two of the toggle positions are used to generate the standard

HBLK interval. However, the additional toggle positions may be

used to generate special HBLK patterns, as shown in Figure 11.

The pattern in this example uses all six toggle positions to

generate two extra groups of pulses during the HBLK inter-

val. By changing the toggle positions, different patterns can

be created.

Horizontal Sequence Control

The AD9948 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 12. The SCP 0 is always hard-

coded to Line 0, and SCP1–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 will define Region 0 for CLPOB, and in that region,

any of the four individual CLPOB sequences may be selected with

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

and in that region each signal can be assigned to a different

individual sequence. The sequence control registers are sum-

marized in Table XIV.

External HBLK Signal

The AD9948 can also be used with an external HBLK signal. Set-

ting the HBLKDIR register (Address x040) to high will disable the

internal HBLK signal generation. The polarity of the external

signal is specified using the HBLKPOL register, and the mask-

ing polarity of H1 is specified using the HBLKMASK register.

Table XV summarizes the register values when using an external

HBLK signal.

Table XIV. Horizontal Sequence Control Parameters for CLPOB, PBLK, and HBLK

Length

Range

Description

SCP

12b

0–4095 Line Number

CLOB/PBLK/HBLK SCP to Define Horizontal Regions 0–3.

SPTR

0–3 Sequence Number

Sequence Pointer for Horizontal Regions 0–3.

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