Datasheet

AD9979
Rev. C | Page 21 of 56
HBLK Mode 2 Operation
HBLK Mode 2 allows more advanced HBLK pattern operation.
If unevenly spaced, multiple areas of HCLK pulses are needed;
therefore, use HBLK Mode 2. Using a separate set of registers,
HBLK Mode 2 can divide the HBLK region into up to six
different repeat areas (see Table 11). As shown in Figure 28,
each repeat area shares a common group of toggle positions,
HBLKSTARTA, HBLKSTARTB, and HBLKSTARTC. However, the
number of toggles following each HBLKSTARTA, HBLKSTARTB,
and HBLKSTARTC position can be unique in each repeat area
by using RAxHyREPz, where x represents the repeat area, from 0
to 5, y represents the horizontal driver, 1 or 2, and z represents the
HBLK repeat area start position for HBLK Mode 2, A, B, or C.
As shown in Figure 29, setting the RAxH1REPA/RAxH1REPB/
RAxH1REPC or RAxH2REPA/RAxH2REPB/RAxH2REPC
registers to 0 masks the HCLK groups from appearing in a
particular repeat area. Figure 28 shows only two repeat areas
being used, although up to 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 28 shows the 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. HBLKSTARTA, HBLKSTARTB, and
HBLKSTARTC, as well as RAxH1REPA/RAxH1REPB/
RAxH1REPC and RAxH2REPA/RAxH2REPB/RAxH2REPC,
define operation for the even lines. For separate control of the
odd lines, the HBLKALT_PATx 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.
HBLK
H1
H2
HBLKSTART
HBLKSTARTA
HBLKEND
HBLKLEN
REPEAT AREA 0
HBLKREP = 2
TO CREATE 2 REPEAT AREAS
HD
REPEAT AREA 1
HBLKSTARTB
HBLKSTARTC
RA0H1REPA
RA0H1REPB RA0H1REPC
ALL RAxHyREPz REGISTERS = 2, TO CREATE 2 HCLK PULSES
RA1H1REPA
RA1H1REPB RA1H1REPC
RA0H2REPA
RA0H2REPB RA0H2REPC
RA1H2REPA
RA1H2REPB RA1H2REPC
05957-031
Figure 28. HBLK Mode 2 Registers
H1
H2
HBLKSTART
A
HBLKEND
REPEAT AREA 0
HD
B
C
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 RAxHyREPz = 0
CHANGE NUMBER OF A, B, C PULSES IN ANY
REPEAT AREA USING RAxHyREPz REGISTERS
CREATE UP TO 3 GROUPS OF TOGGLES
A, B, C COMMON IN ALL REPEAT AREAS
0
5957-030
Figure 29. HBLK Mode 2 Operation