AD9992 Datasheet, PDF (58/92 Pages) Analog Devices – 12-Bit CCD Signal Processor with Precision Timing Generator

AD9992
MANUAL SHUTTER OPERATION USING
ENHANCED SYNC MODES
The AD9992 also supports an external signal to control exposure,
using the SYNC input. Generally, the SYNC input is used as an
asynchronous reset signal during master mode operation. When
the enhanced SYNC mode is enabled, the SYNC input provides
additional control of the exposure operation.
Normal SYNC Mode (Mode 1)
By default, the SYNC input is used in master mode for syn-
chronizing the internal counters of the AD9992 with external
timing. The SYNC During Master Mode Operation section
describes how horizontal, vertical, and field designator signals are
reset by the rising edge of the SYNC pulse. Figure 66 also shows
how this mode operates, highlighting the behavior of the mode
field designator.
Enhanced SYNC Modes (Mode 2 and Mode 3)
The enhanced SYNC modes can be used to accommodate unique
synchronization requirements during exposure operations. In
SYNC Mode 2, the V and VSG outputs are suspended and the
VD output is masked. The V-outputs are held at the dc value
established by the Sequence 0 start polarities. There is no SCP
operation, but the H-counter is still enabled. Finally, the AFE
sampling clocks HD, H/RG, CLPOB, and HBLK are operational
and use Sequence 0 behavior. See Figure 67 for more details.
Set Register ENH_ SYNC_EN (Address 0x13 Bit 3) to 1 to
enable the enhanced SYNC modes
Mode 3 uses all of these features, but the V-outputs are continuous
through the SYNC pulse interval. VD control pulses are masked
during the SYNC interval, and the HD pulse can also be masked
if required (see Figure 68).
It is important to note that in both of these enhanced modes,
the SYNC pulse resets the counters at both the falling edge and
the rising edge of the SYNC pulse.
Register Update and Field Designator
When using special SYNC Mode 2 or SYNC Mode 3, the VD-
updated registers, such as PRIMARY_ACTION, are not
updated during the SYNC interval, and the SCP0 function is
ignored and held at 0 (see Figure 69).
When using SYNC Mode 2 or SYNC Mode 3, both the rising and
falling edges increment the internal field designator; therefore,
the new register data takes effect and VTP information is
updated to new SEQ0 data. However, this does not occur if the
MODE register creates an output of one field. In that case,
the region, sequence, and group information does not change
(see Figure 70).
Shutter Operation in SLR Mode
Referring to Figure 71,
1. To turn on VSUB, write to the appropriate GP registers to
start VSUB and manual exposure [PRIMARY_ACTION = 5].
This change takes effect after the next VD. SUBCK is sup-
pressed during the exposure and readout phases.
2. To turn on MSHUT during the interval between the next
VD and SYNC, write to the appropriate GP register. When
MSHUT is in the on position, it has line and pixel control.
This change takes effect on the SYNC falling edge because
there is an internal VD.
3. If the MODE register is programmed to cycle through
multiple fields (5, 7, 3, 5, 7, 3, …, in this example), the internal
field designator increments. If the MODE register is not
required to increment, set up the MODE register such that it
outputs only one field. This prevents the MODE counter
from incrementing during the SYNC interval.
4. Write to the manual readout trigger to begin the manual
readout [PRIMARY_ACTION = 6]. Write to the appropriate
GP registers to trigger MSHUT to toggle low at the end of
the exposure. This change takes effect on the SYNC rising
edge during readout. Because VD register update is
disabled, the trigger takes effect on the SYNC rising edge.
The MSHUT falling edge is aligned to the SYNC rising
edge. Because the MSHUT falling edge is aligned with VD,
it may be necessary to insert a dummy VD to delay the
readout.
Note that because the internal exposure counter (PRIMARY
counter) is not used during manual SYNC mode operation and
the VD register update is disabled, control is lost on the fine
placement of the GP signals for VSUB, MSHUT, and STROBE
edges while SYNC is low.
New Serial Registers
SYNC Mode 2 and SYNC Mode 3 are controlled using the registers
listed in Table 25. Note that registers for enhanced SYNC modes
are located at Address 0x13 Bits [6:3].
Table 25. Registers for Enhanced SYNC Modes
Register
Length Description
ENH_SYNC_EN
1b
HI active to enable
(default LO)
SYNC_MASK_V
1b
HI active to enable masking
(default LO)
SYNC_MASK_VD 1b
HI active to enable masking
(default HI)
SYNC_MASK_HD 1b
HI active to enable masking
(default HI)
Rev. C | Page 58 of 92