AD9927 Analog Devices, AD9927 Datasheet - Page 66

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

AD9927
MANUAL SHUTTER OPERATION USING
ENHANCED SYNC MODES
The AD9927 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
synchronizing the internal counters of the AD9927 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 79
also shows how this mode operates, highlighting the behavior of
the mode field designator.
Enhanced SYNC Modes (Modes 2 and 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, HBLK,
are operational and use Sequence 0 behavior. See Figure 80 for
more details.
To enable the enhanced SYNC modes, set the register
ENH_SYNC_EN (Address 0x13 Bit [3]) to 1.
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 81).
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 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 82).
When using either SYNC Mode 2 or 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 is
to create an output of one field. In that case, the region, sequence,
and group information does not change (see Figure 83).
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Shutter Operation in SLR Mode
Referring to Figure 84,
1.
2.
3.
4.
Note that since 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 Modes 2 and 3 are controlled using the registers listed
in Table 44.
Table 44. Registers for Enhanced SYNC Modes
Register
ENH_SYNC_EN
SYNC_MASK_V
SYNC_MASK_VD
SYNC_MASK_HD
Note that registers for enhanced SYNC modes are located at
Address 0x13 Bits [6:3].
To turn on VSUB, write to the appropriate GP registers to
trigger VSUB and start the manual exposure
[PRIMARY_ACTION = 5]. This change takes effect after
the next VD, and SUBCK is suppressed during the
exposure and readout phases.
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 since
there is an internal VD.
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.
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. Since 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.
Length
1b
1b
1b
1b
Description
HI active to enable
(default LO)
HI active to enable masking
(default LO)
HI active to enable masking
(default HI)
HI active to enable masking
(default HI)