Metrologic IS4910 Series, Руководство программиста

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1
IS4910 S
YSTEM
H
ARDWARE
A
RCHITECTURE
Figure 1 :
IS4910 System Hardware Architecture
Communication with the image sensor is done over two buses – the control bus ( I
2
C ) and the data bus.
The control bus is used to send commands to the image sensor, and the data bus is used to transfer
images from the image sensor to the host system.
The image sensor can operate in two modes – snapshot mode and video mode.
•
In snapshot mode , the image sensor acquires and transfers a single image.
The IS4910 illumination system can be used to illuminate (flash) an object.
•
In video mode , the image sensor continuously acquires and transfers images, row by row.
The IS4910 illumination system can either be constantly ON or OFF during the image acquisition
in video mode.
The Trigger signal is used to initiate image acquisition in snapshot mode. The Trigger signal is also
connected to the Illumination system, thus, automatically initiating the flash illumination. Duration of the
flash and the image sensor’s exposure to it depends on the duration of the Trigger pulse, which is
controlled by software. Actual duration of the flash also depends on such signals as Minimum
Illumination (Illum_ON), controlled by software, and the signal from the First
Flash
®
hardware circuitry.
In video mode, the Trigger signal is always de-asserted. Image acquisition in video mode is initiated by a
command sent to the image sensor by software over control bus (
I
2
C ). Illumination in video mode can be
constantly kept on or off by keeping the signal Minimum Illumination (Illum_ON) on or off.
For more details on IS4910 hardware system, please refer to the IS4910 User Manual.