AD9925 Datasheet, PDF (25/96 Pages) Analog Devices – CCD Signal Processor with Vertical Driver and Precision Timing Generator

Masking Using FREEZE/RESUME Registers
As shown in Figure 33, the FREEZE/RESUME registers are used
to temporarily mask the XV outputs. The pixel locations to
begin the masking (FREEZE) and end the masking (RESUME)
create an area in which the vertical toggle positions are ignored.
At the pixel location specified in the FREEZE register, the XV
outputs will be held static at their current dc state, high or low.
The XV outputs are held until the pixel location specified by the
AD9925
RESUME register is reached, at which point the signals will
continue with any remaining toggle positions. Two sets of
FREEZE/RESUME registers are provided, allowing the vertical
outputs to be interrupted twice in the same line. The FREEZE
and RESUME positions are programmed in the vertical pattern
group registers, but are enabled separately using the VMASK
registers. The VMASK registers are described in the Vertical
Sequences (VSEQ) section.
HD
NO MASKING AREA
XV1
XV8
Figure 32. No Vertical Masking
HD
FREEZE
MASKING AREA
FOR XV1 TO XV8
RESUME
XV1
XV8
NOTES
1. ALL TOGGLE POSITIONS WITHIN THE FREEZE/RESUME MASKING AREA ARE IGNORED. H-COUNTER CONTINUES TO COUNT DURING MASKING.
2. TWO SEPARATE MASKING AREAS ARE AVAILABLE FOR EACH VPAT GROUP, USING FREEZE1/RESUME1 AND FREEZE2/RESUME2 REGISTERS.
Figure 33. Vertical Masking Using the FREEZE/RESUME Registers
Rev. A | Page 25 of 96