Camera Interface
7-10
The clock divider also allows disabling the external clock by setting the
CAMEXCLK_EN bit.
7.2.1.7
Interrupt Generator
The interrupt generator handles six cases of interrupt:
-
Data transfer interrupt. One IRQ is generated per word received.
-
HSYNC rising edge (start of frame)
-
HSYNC falling edge (end of frame)
-
VSYNC rising edge (start of image)
-
VSYNC falling edge (end of image)
-
FIFO overflow
Each case is registered by activating (high) one of the six interrupt register bits
to indicate the origin of the interrupt. However, the interrupt mask register can
disable the source of the interruption.
Only one line of interrupt is used to ask for a read of the interrupt register. When
the read occurs, the register is automatically reset and the interrupt signal is
released.
Figure 7-9. IRQ Generated on VSYNC Falling Edge
ÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
VSYNC
MCLK
RNW, CS
CAM_NIRQ
7.2.1.8
DMA Procedure
A typical procedure to perform the data transfer by DMA is as follows:
1) Rising edge of VSYNC sends an interrupt to TI925T to alert the system
DMA that a start of image has occurred. The system DMA is programmed
to move one complete image of data then give an interrupt when complete.
2) High level of HSYNC and proper clock edge start the first data transfer
from the camera to the OMAP5910 camera interface. After the first two
pixels of data are received (8 bits x 4 transfers = 32 bits), a DMA request
is made. The system DMA moves the 32-bit data to a predefined SDRAM
location.