5-11
Application Notes
Image Acquisition Procedure
summarizes the Mode 1 imaging acquisition procedure.
summarizes
the Mode 1 input and output signal functions.
As with Mode 3, VREF and HREF indicate the reading of valid vertical and horizontal pixel
data, respectively. When both signals are high, the 8-bit pixel data, Pix_D0 through Pix_D7,
should be read out on each positive edge of PCLK.
In Mode 1, set the exposure time by programming an I
2
on page 5-16). Once programmed, the duration is set for the exposure time during
the next frame, which is read out in the subsequent frame. As with Mode 3, the gain is set
via I
2
C registers. Once programmed, the subsequent frame is transferred with the new
gain. Use auto exposure and auto gain modes to simplify the process. The signal UV6
indicates when the SE4400 is exposing. The signal is brought high during the exposure
time and is held low the remainder of the frame.
In Mode 1, the EXSFT line is used only to control the focusing motor (see
page 5-16). Also, if the focus motor position was altered, a 20 ms settling time must pass
before the exposure period can begin, meaning that for each frame in which the focus was
changed, the exposure time cannot exceed a frame time minus 20 ms.
Table 5-2. Mode 1 Signal Function Summary
Signal
Name
I/O
Function
Significance of
Negative Edge
Significance of
Positive Edge
Comment
UV6
O
Indicates
exposure time.
Indicates the CCD
has stopped
exposing.
Indicates the
CCD has begun
exposing.
The period between
successive negative
edges is called a
frame.
VREF
O
Signifies when
valid vertical lines
are being read.
Reading of valid
vertical lines is
complete.
Reading of valid
vertical lines has
begun.
HREF
O
Signifies when
valid part of
horizontal line is
being read.
Reading of valid
part of line is
complete.
Reading of valid
part of line has
begun.
The period of HREF is
known as a line time
and is denoted "H".
PCLK
O
Pixel clock.
None
Indicates the
8-bit pixel data is
available to be
read out.
The period of PCLK is
denoted "T".
Summary of Contents for Symbol SE4400
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