AR0833 Datasheet, PDF (51/64 Pages) ON Semiconductor – 8 Mp CMOS Digital Image Sensor

AR0833: 1/3.2-Inch 8 Mp CMOS Digital Image Sensor
Integration Time for Interlaced HDR Readout
global_read_start = 216  global_read_start27:0 + global_read_start115:0
(EQ 15)
global_shutter_start = 216  global_shutter_start27:0 + global_shutter_start115:0 (EQ 16)
The integration equation allows for 24-bit precision when calculating both the shutter
and readout of the image. The global_rst_end has only 16-bit as the array reset function
and requires a short amount of time.
The integration time can also be scaled using global_scale. The variable can be set to
0–512, 1–2048, 2–128, and 3–32.
These programming restrictions must be met for correct operation of bulb exposures:
• global_read_start > global_shutter_start
• global_shutter_start > global_rst_end
• global_shutter_start must be smaller than the exposure time (that is, this counter
must expire before the trigger is de-asserted)
Figure 39: Global Reset Bulb
Trigger
Wait for end of current row
ERS Row Reset
global_rst_end
Integration
GPI2
Automatic at end of frame readout
Readout ERS
global_read_start - global_shutter_start
Retriggering the Global Reset Sequence
The trigger for the global reset sequence is edge-sensitive; the global reset sequence
cannot be retriggered until the global trigger bit (in the R0x315E global_seq_trigger
register) has been returned to “0,” and the GPI (if any) associated with the trigger func-
tion has been negated.
The earliest time that the global reset sequence can be retriggered is the point at which
the SHUTTER output negates; this occurs approximately (2 * line_length_pck) after the
negation of FV for the global reset readout phase.
Using Global Reset with SMIA Data Path
When a global reset sequence is triggered, it usually results in the frame in progress
being truncated (at the end of the current output line). The SMIA data path limiter func-
tion (see Figure 40 on page 52) attempts to extend (pad) all frames to the programmed
value of y_output_size. If this padding is still in progress when the global reset readout
phase starts, the SMIA data path will not detect the start of the frame correctly. There-
fore, to use global reset with the serial data path, this timing scenario must be avoided.
One possible way of doing this would be to synchronize (under software control) the
assertion of trigger to an end-of-frame marker on the serial data stream.
At the end of the readout phase of the global reset sequence, the sensor automatically
resumes operation in ERS mode.
AR0833_DS Rev. H Pub. 4/15 EN
51
©Semiconductor Components Industries, LLC, 2015.