IBIS4-1300_09 Datasheet, PDF (21/37 Pages) Cypress Semiconductor – 1.3 MPxl Rolling Shutter CMOS Image Sensor

IBIS4-1300
Figure 15. shows a typical operation mode of the image
sensor.
At the start of a new frame, the device may be (re-)configured.
If necessary, the output amplifier gain and offset are adjusted
or the device is put in viewfinder mode.
Then, the frame readout shift register is initiated by pulsing
"SYNC_YR". This pulse occurs once per frame, normally as a
part of the first row blanking sequence.
The readout of a row (line) starts with row blanking initialization
sequence. Here several pulses are applied for Y-direction
shift, the column amplifier S&H and nulling, and the start
(SYNC_X) of the X-direction shift register.
The frame reset shift register is started also once per frame by
"SYNC_YL", this pulse occurs once per frame, normally as a
part of the row blanking sequence of one particular row. The
time delay from the SYNC_YL to SYNC_YR is the integration
time. The integration is thus a multiple of the row readout time.
The reset shift register always leads the readout shift register.
Therefore, the integration time should be determined before
the start of the frame readout. The value that is fixed at that
moment will be the integration time of the NEXT frame. If the
value set for the integration time changes during frame
readout, the start pulse might be lost and the next frame might
be invalid. We will now discuss all steps in more detail.
Set configuration
Configuration of the image sensor implies control &
adjustment of the following points:
• output amplifier offset level, set by 'dac_bit[0...3]'
• output amplifier gain setting, set by 'gc_bit[0...3]'
• choose the integration time of the next frame
• set/clear viewfinder mode (pin 'subsampl')
• in case when the fast adjustment of the offset level is used,
plus 'calib_f' and 'unitygain' as described before in figures
Figure 7. and Figure 8.
Viewfinder mode vs. normal readout
Table 8. co-ordinate of the row or column selected by the Y/X shift registers after a # clock periods in viewfinder mode
and full image mode
Clock
Sync
1
2
3
4
5
6
Viewfinder mode
None
None
Row 1
Row 5
Row 9
Row 13 Row 17
Y reg.
Dark
Col. 1
Col. 5
Col. 9
Col. 13
X reg.
Full image mode
None
None
Row 1
Row 2
Row 3
Row 4
Row 5
Y reg.
Dark
Col. 1
Col. 2
Col. 3
Col. 4
X reg.
Clock
Viewfinder mode
258
Row 1025
259
Row 1029
260
EOS
322
Col. 1281
323
Col. 1285
324
EOS Dark
Clock
Full image mode
1030
1031
Row 1029 Row 1030
Y shift register
1032
EOS
In full image readout mode (pin 84, subsmpl = 0), the imager
is a 1280 x 1024 SXGA image sensor. There are 3 dummy
pixels read at all 4 borders of the image.
In viewfinder mode (subsmpl = 1), the imager acts as a 320 x
256 QVGA image sensor with one dummy pixel at the start of
a row/column.
Table 8. shows which column or row is selected after a
number of clock pulses.
1287
1288
1289
Col. 1285 Col. 1286 EOS Dark
X shift register
Start of the Y shift registers for row readout & row reset
The shift registers are put in their initial state by a
synchronization- or start pulse. (sync_x, sync_yr, sync_yl).
The synchronization signal is low-active and should only be
generated when the clock of the shift register is high. After the
synchronization pulse, two falling clock edges are needed to
skip dummy pixels/lines. On every falling clock edge, the shift
register selects a new row for readout or reset. Figure 16.
shows this timing.
Document Number: 38-05707 Rev. *B
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