AD9927 Analog Devices, AD9927 Datasheet - Page 20

• Manufacturer Part Number: AD9927
• Description: 14-Bit CCD Signal Processor
• Manufacturer: Analog Devices

AD9927
HORIZONTAL CLAMPING AND BLANKING
The AD9927’s horizontal clamping and blanking pulses are fully
programmable to suit a variety of applications. Individual
control is provided for CLPOB, PBLK, and HBLK in the
different regions of each field. This allows the dark pixel
clamping and blanking patterns to be changed at each stage of
the readout in order to accommodate different image transfer
timing and high speed line shifts.
Individual CLPOB and PBLK Patterns
The AFE horizontal timing consists of CLPOB and PBLK, as
shown in Figure 23. These two signals are programmed
independently using the registers in Table 10. The start polarity
for the CLPOB (and PBLK) signal is CLPOBPOL (PBLKPOL),
and the first and second toggle positions of the pulse are
CLPOBTOG1 (PBLKTOG1) and CLPOBTOG2 (PBLKTOG2).
Both signals are active low and should be programmed
accordingly.
A separate pattern for CLPOB and PBLK can be programmed
for each vertical sequence. As described in the Vertical Timing
Generation section, several V-sequences can be created, each
containing a unique pulse pattern for CLPOB and PBLK. Figure 49
shows how the sequence change positions divide the readout field
into different regions. By assigning a different V-sequence to
each region, the CLPOB and PBLK signals can change with
each change in the vertical timing.
Table 10. CLPOB and PBLK Pattern Registers
Register
CLPOBPOL
PBLKPOL
CLPOBTOG1
CLPOBTOG2
PBLKTOG1
PBLKBTOG2
CLPMASKSTART
CLPMASKEND
PBLKMASKSTART
PBLKMASKEND
Length
1b
1b
13b
13b
13b
13b
13b
13b
13b
13b
Range
High/low
High/low
0 to 8191 pixel location
0 to 8191 pixel location
0 to 8191 pixel location
0 to 8191 pixel location
0 to 8191 line location
0 to 8191 line location
0 to 8191 line location
0 to 8191 line location
Description
Starting polarity of CLPOB for each V-sequence.
Starting polarity of PBLK for each V-sequence.
First CLPOB toggle position within line for each V-sequence.
Second CLPOB toggle position within line for each V-sequence.
First PBLK toggle position within line for each V-sequence.
Second PBLK toggle position within line for each V-sequence.
CLPOB masking area—starting line within field (maximum of three areas).
CLPOB masking area—ending line within field (maximum of three areas).
PBLK masking area—starting line within field (maximum of three areas).
PBLK masking area—ending line within field (maximum of three areas).
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CLPOB and PBLK Masking Areas
Additionally, the AD9927 allows the CLPOB and PBLK signals to
be disabled in certain lines in the field without changing any of
the existing CLPOB pattern settings.
To use CLPOB (or PBLK) masking, the CLPMASKSTART
(PBLKMASKSTART) and CLPMASKEND (PBLKMASKEND)
registers are programmed to specify the start and end lines in
the field where the CLPOB (PBLK) patterns are ignored. The
three sets of start and end registers allow up to three CLPOB
(PBLK) masking areas to be created.
The CLPOB and PBLK masking registers are not specific to a
certain V-sequence; they are always active for any existing field
of timing. During operation, to disable the CLPOB masking
feature, these registers must be set to the maximum value of
0x1FFF or a value greater than the programmed VD length.
Note that to disable CLPOB (and PBLK) masking during power-up,
it is recommended to set CLPMASKSTART (PBLKMASKSTART)
to 8191 and CLPMASKEND (PBLKMASKEND) to 0. This
prevents any accidental masking caused by register update events.