AD9974BBCZ datasheet(23/52 Pages) AD

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AD9974

Rev. A | Page 23 of 52

HBLK Mode 2 Operation

HBLK Mode 2 allows more advanced HBLK pattern operation.

If unevenly spaced HCLK pulses in multiple areas are needed,

HBLK Mode 2 can be used. Using a separate set of registers,

HBLK Mode 2 can divide the HBLK region into up to six repeat

areas (see Table 12). As shown in Figure 31, each repeat area

shares a common group of toggle positions, HBLKSTARTA,

HBLKSTARTB, and HBLKSTARTC. However, the number of

toggles following each start position can be unique in each

repeat area by using the RAH1REP and RAH2REP registers.

As shown in Figure 30, setting the RAH1REPA/RAH1REPB/

RAH1REPC or RAH2REPA/RAH2REPB/RAH2REPC registers

to 0 masks HCLK groups from appearing in a particular repeat

area. Figure 31 shows only two repeat areas being used, although

six are available. It is possible to program a separate number of

repeat area repetitions for H1 and H2, but generally the same

value is used for both H1 and H2.

Figure 31 shows the following example:

RA0H1REPA/RA0H1REPB/RA0H1REPC =

RA0H2REPA/RA0H2REPB/RA0H2REPC =

RA1H1REPA/RA1H1REPB/RA1H1REPC =

RA1H2REPA/RA1H2REPB/RA1H2REPC = 2.

Furthermore, HBLK Mode 2 allows a different HBLK pattern

on even and odd lines. The HBLKSTARTA, HBLKSTARTB, and

HBLKSTARTC registers, as well as the RAH1REPA/RAH1REPB/

RAH1REPC and RAH2REPA/RAH2REPB/RAH2REPC registers,

define operation for the even lines. For separate control of the

odd lines, the HBLKALT_PAT registers specify up to six repeat

areas on the odd lines by reordering the repeat areas used for the

even lines. New patterns are not available, but the order of the

previously defined repeat areas on the even lines can be changed

for the odd lines to accommodate advanced CCD operation.

HBLKSTART

HBLKEND

REPEAT AREA 0

REPEAT AREA 1

REPEAT AREA 2

REPEAT AREA 3

REPEAT AREA 4

REPEAT AREA 5

MASK A, B, C PULSES IN ANY REPEAT

AREA BY SETTING RA*H*REP* = 0

CHANGE NUMBER OF A, B, C PULSES IN ANY

REPEAT AREA USING RA*H*REP* REGISTERS

CREATE UP TO 3 GROUPS OF TOGGLES

A, B, C COMMON IN ALL REPEAT AREAS

Figure 30. HBLK Mode 2 Operation

HBLK

HBLKSTART

HBLKSTARTA

HBLKEND

HBLKLEN

REPEAT AREA 0

HBLKREP = 2

TO CREATE 2 REPEAT AREAS

REPEAT AREA 1

HBLKSTARTB

HBLKSTARTC

RA0H1REPA RA0H1REPB

RA0H1REPC

ALL RA*H*REPA, B, C REGISTERS = 2, TO CREATE 2 HCLK PULSES

RA1H1REPA RA1H1REPB

RA1H1REPC

RA0H2REPA RA0H2REPB

RA0H2REPC

RA1H2REPA RA1H2REPB

RA1H2REPC

Figure 31. HBLK Mode 2 Registers

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