PDF: 4749051511/Source:7788125767
Aptina reserves the right to change products or specifications without notice.
MT9T111_DG - Rev. B 9/10 EN
53
©2007 Aptina Imaging Corporation. All rights reserved.
MT9T111: Developer Guide
JPEG Encoder
Preliminary
Adaptive Clock Switching
The adaptive clock switching feature is implemented on the parallel output interface for
continuous and spoof mode, but is not supported for bypass mode.
When ob_tx_control.en_adaptive_clk is enabled, the hardware automatically switches
clocks according to FIFO fullness status.
Three clock dividers are implemented for PCLK1, PCLK2, and PCLK3 in their associated
configuration registers (0x3C66, 0x3C88, 0x3C8A). To utilize this feature, PCLK1 should
be configured as the slowest clock (for example, divider = 6), PCLK2 should be the
second slowest (for example, divider = 3), and PCLK3 should be the fastest clock (for
example, divider = 1).
After reset, the output PCLK stays at PCLK1. It switches to PCLK2 when the FIFO reaches
50 percent full, switches to PCLK3 when FIFO reaches 75 percent full, or to PCLK1 when
FIFO drops below 25 percent full. If the output buffer is currently using PCLK3, it will
switch to PCLK2 when the FIFO is below 50% full. The switching criteria is summarized
in Table 20.
Table 20:
Clock Switching Criteria
Fullness/Selection
PCLK1
PCLK2
PCLK3
25%
Stay at PCLK1
Switch to PCLK1
N/A
50%
Switch to PCLK2
Stay at PCLK2
Switch to PCLK2
75%
N/A
Switch to PCLK3
Stay at PCLK3