AD9927 Analog Devices, AD9927 Datasheet - Page 64

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

AD9927
COMPLETE EXPOSURE/READOUT OPERATION
USING PRIMARY COUNTER AND GPO SIGNALS
Figure 78 demonstrates a typical expose/read cycle while exercising
the GPO signals. Using a 3-field CCD with an exposure time
that is greater than one field but less than two fields in duration,
requires a total of five fields for the entire exposure/readout
operation. Other exposure times and other CCD field config-
urations require modification of these example settings.
Note that if the MODE registers are changed to be VD updated,
as shown in the MODE Registers section and in Figure 66, the
MODE update will be delayed by one additional field. This should
be accounted for in selecting the number of fields to cycle and
which VD location to write to the MODE registers.
1.
The primary counter is used to control the masking
of VSG and SUBCK during exposure/readout. The
PRIMARY_MAX register should be set equal to the
total number of fields used for exposure and readout.
In this example, PRIMARY_MAX = 5.
The SUBCK masking should not occur immediately at
the next VD edge (Step 2), because this would define an
exposure time that begins in the previous field. Write to
the PRIMARY_DELAY register to delay the masking of
VSG and SUBCK pulses in the first exposure field. In this
example, MASKDELAY = 1.
Write to the SUBCKMASK_NUM register (Address 0x74)
to specify the number of fields to mask SUBCK while the
CCD data is read. In this example, SUBCKMASK_NUM = 4.
Write to the SGMASK_NUM register (Address 0x74) to
specify the number of fields to mask VSG outputs during
exposure. In this example, SGMASK_NUM = 1.
Write to the PRIMARY_ACTION register (Address 0x70)
to trigger the GP1 (STROBE), GP2 (MSHUT), and GP3
(VSUB) signals and to start the expose/read operation.
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2.
3.
4.
5.
6.
7.
8.
9.
10. VD/HD falling edge updates the serial writes from 9. VSG
Write to the MODE registers to configure the next five
fields. The first two fields during exposure are the same as
the current draft mode fields, and the following three fields
are the still-frame readout fields. The register settings for
the draft mode field and the three readout fields are
previously programmed. Note that if the MODE registers
are changed to VD updated, only one field of exposure
should be included (the second one) because the MODE
settings will be delayed an extra field.
VD/HD falling edge updates the serial writes from 1.
GP3 (VSUB) output turns on at the field/line/pixel specified.
VSUB Example 1 and Example 2 use GP3TOG1_FD = 1.
GP1 (STROBE) output turns on and off at the location
specified.
GP2 (MSHUT) output turns off at the location specified.
The next VD falling edge automatically starts the first
read field.
The next VD falling edge automatically starts the second
read field.
The next VD falling edge automatically starts the third
read field.
Write to the MODE register to reconfigure the single draft
mode field timing. Note that if the MODE registers are
changed to VD updated, this write should occur one field
earlier.
outputs return to draft mode timing. SUBCK output
resumes operation. GP2 (MSHUT) output returns to the
on position (active or open). GP3 (VSUB) output returns
to the off position (inactive).