AD9927BBCZ datasheet(22/100 Pages) AD

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AD9927

Rev. 0 | Page 22 of 100

Individual HBLK Patterns

The HBLK programmable timing shown in Figure 25 is similar

to CLPOB and PBLK; however, there is no start polarity control.

Only the toggle positions are used to designate the start and

stop positions of the blanking period. Additionally, there are

separate masking polarity controls for H1, H2, and HL that

designate the polarity of the horizontal clock signals during the

blanking period. Setting HBLKMASK_H1 high sets H1, and

therefore H3, H5, and H7, low during the blanking, as shown in

Figure 26. As with the CLPOB and PBLK signals, HBLK

registers are available in each V-sequence, allowing different

blanking signals to be used with different vertical timing

sequences.

The AD9927 supports three modes of HBLK operation. HBLK

Mode 0 supports basic operation and some support for special

HBLK patterns. HBLK Mode 1 supports pixel mixing HBLK

operation. HBLK Mode 2 supports advanced HBLK operation.

The following sections describe each mode in detail. Register

parameters are described in detail in Table 11.

HBLK Mode 0 Operation

There are six toggle positions available for HBLK. Normally,

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 27. 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.

Separate toggle positions are available for even and odd lines. If

alternation is not needed, the same values should be loaded into

the registers for even (HBLKTOGE) and odd (HBLKTOGO) lines.

HBLK

BASIC HBLK PULSE IS GENERATED USING HBLKTOGE1 AND HBLKTOGE2 REGISTERS (HBLKALT = 0)

BLANK

HBLKTOGE1

HBLKTOGE2

Figure 25. Typical Horizontal Blanking Pulse Placement (HBLKMODE = 0)

HBLK

H1/H3/H5/H7

H2/H4/H6/H8

THE POLARITY OF H1/H3/H5/H7 DURING BLANKING IS PROGRAMMABLE

(H2/H4/H6/H8 AND HL ARE SEPARATELY PROGRAMMABLE)

Figure 26. HBLK Masking Polarity Control

HBLK

SPECIAL H-BLANK PATTERN IS CREATED USING MULTIPLE HBLK TOGGLE POSITIONS (HBLKALT = 0)

H1/H3

H2/H4

HBLKTOGE1

HBLKTOGE2

HBLKTOGE3

HBLKTOGE4

HBLKTOGE5

HBLKTOGE6

Figure 27. Using Multiple Toggle Positions for HBLK (HBLKMODE = 0)

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