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AT32F435/437
Series Reference Manual
2022.11.11
Page 641
Rev 2.03
data (DVP_D) output from the CMOS video camera. The DVP_PCLK is provided by the CMOS video
camera. Data can be captured on either the rising or the falling edge of the DVP_PCLK by setting the
CKP bit in the DVP_CTR register. The captured data can be divided into two parts: valid pixel data and
blanking period data. The user only concerns the former. The CMOS can deliver synchronization
information in a single or multiple modes for the receiver to perform frame segmentation and fetch valid
pixel data. The digital video parallel interface (DVP) supports hardware or embedded code
synchronization, which can be done through the SM bit in the DVP_CTRL register.
27.3.1 Hardware synchronization mode
In this mode, the CMOS video camera offers two synchronization signals: horizontal and vertical
synchronization signals. The hardware synchronization mode is selected by setting SM=0 in the
DVP_CTRL register. The horizontal synchronization signals are used to distinguish the valid pixel and
blanking periods, and it is activated by the DVP_HSYNC pin to enable DVP to split lines and fetch valid
pixel data. The polarity of the horizontal synchronization signals can be programmed through the HSP
bit in the DVP_CTRL register in order to ensure that it matches the output of the digital video camera.
The vertical synchronization signals are used for interframe separation, and it is activated by the
DVP_VSYNC pin to enable DVP to split frames. The vertical synchronization signals are expressed in
two types.
Frame start
In this mode, the vertical synchronization signals are used as a frame start signal. The Frame start signal
indicates the end of the current frame and the start of the next frame. The polarity of the Frame start
signal is programmable through the VSP bit in the DVP_CTRL register to ensure that it matches the
output of the digital video camera. For example, in Figure 27-2, the VSP bit must be set (the
DVP_VSYNC high level marks the Frame start).
Figure 27-2 CMOS video camera output in Frame start type
DVP_PCLK
DVP_VSYNC
DVP_HSYNC
DVP_D
blanking
blankin
g
blanking
Frame valid
In this mode, the vertical synchronization signals are used to determine whether the captured data is in
the vertical blanking period. Frames are split through the vertical blanking period. Similarly, the VSP bit
in the DVP_CTR register can be used to program the polarity of the frame valid to ensure that it matches
the output of the digital video camera. For example, in Figure 27-3, the VSP bit must be set to 0
(DVP_VSYNC low level indicates that the captured data is in the vertical blanking period).
Figure 27-3 CMOS video camera output in Frame valid type
DVP_PCLK
DVP_VSYNC
DVP_HSYNC
DVP_D
vertical
blanking
horizontal
blanking
horizontal
blanking
horizontal
blanking
vertical
blanking
horizontal
blanking