
NOIL2SM1300A
Master Mode
In this mode, a rising edge on int_time1 pin is used to
trigger the start of integration and read out. The tint_timer
defines the integration time independent of the assertion of
the input pin int_time1. After the integration time counter
runs out, the FOT automatically starts and the image readout
is done. During readout, the image array is kept in reset. A
request for a new frame is started again when a new rising
edge on int_time is detected. The time of the falling edge is
Slave Mode
Integration time control is identical to the pipelined
shutter slave mode. The int_time1 pin controls the start of
integration. When int_time is deasserted, the FOT starts
(analog value on the pixel diode is transferred to the pixel
memory element). Only at that time, image read out can start
(similar to the pipelined read out). During read out, the
image array is kept in reset. A request for a new frame is
started when int_time goes high again.
not important in this mode.
Non Destructive Readout (NDR)
time
Figure 17. Principle of Non Destructive Readout
The sensor can also be read out in a nondestructive
method. After a pixel is initially reset, it can be read multiple
times, without being reset. You can record the initial reset
level and all intermediate signals. High light levels saturate
the pixels quickly, but a useful signal is obtained from the
must be used. Essentially, an active pixel array is read
multiple times, and reset only once. The external system
intelligence interprets the data. Table 14 on page 23
summarizes the advantages and disadvantages of
nondestructive readout.
early samples. For low light levels, the later or latest samples
Table 14. ADVANTAGES AND DISADVANTAGES OF NON DESTRUCTIVE READOUT
Advantages
Low noise, because it is true CDS
High sensitivity. The conversion capacitance is kept low.
High dynamic range. The results include signals for short and long
integration times.
Note that the amount of samples taken with one initial
reset is programmable in the nr_of_ndr_steps register. If
nr_of_ndr_steps is one, the sensor operates in the default
method, that is one reset and one sample. This is called the
Disadvantages
System memory required to record the reset level and the
intermediate samples
Requires multiples readings of each pixel, so there is higher data
throughput
Requires system level digital calculations
When nr_of_ndr_steps is two, there is one reset and two
samples, and so on. In the slave mode, nothing changes on
the protocol of the signals int_time_*. The sequencer
suppresses the internal reset signal to the pixel array.
disable nondestructive read out mode.
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