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Theory of Operation
Revision 1.1
Phoenix PC-1280 USB Digital Camera User’s Guide
Figure 4.2: Phoenix Camera Software Block Diagram
The software supports both single and continuous frame capture. In
either case, the capture can be started by software or by a Trigger
signal. Capturing a sequence of frames is also supported by the
software. The user can specify the number of frames and the inter-
val (in terms of frames) between two consecutively captured
frames. For a small sequence, the driver may be able to allocate the
needed frame buffers within the kernel pool. All sequence frames
will then be captured in the buffer chain. The user can get the frame
after the sequence is complete. However, if the number of frames
in the sequence is too large to be allocated in the kernel pool, the
user must allocate the buffer chain in user mode space, and copy the
sequence frames into the buffer chain. Since the driver still pro-
vides a small buffer chain, there will be no data loss, even when the
USB Bus has other traffic.
Several events may be sent from the DLL to the user application to
indicate certain conditions, such as Trigger, Frame Sync, Frame
Capture is Done and/or Frame Data Transfer is Done. These can be
U S B H o s t
C o n t r o l l e r ( H / W )
A p p l i c a t i o n S / W
U S B
D r i v e r
Phoenix DLL
Phoenix Drive r
MuTech SW
TWAIN
Driver
Other
Drivers
M i c r o s o f t S W
L e g e n d s :
P C 1 2 8 0 S W . C F L
R E V . 1 . 0 1 1 / 1 7 / / 0 4
U s e r
M o d e
K e r n e l
M o d e