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9-36
Video Interface
9.11 Display Freeze
The host can write to the Freeze Mode bits of Register 275 (
page 4-62
)
to select one of the three freeze modes listed in
Table 9.10
.
When the host issues a freeze, the display freezes in the requested
mode and picture reconstruction is halted to prevent overwriting the
stored image. When the host removes the freeze condition, the Display
Controller displays one more field of the current frame and picture
reconstruction is resumed.
Figure 9.18
shows the timing of the freeze modes. When the host issues
a Freeze Frame request, the Display Controller repeats both the first and
last field of the frame store. After the freeze is removed, the Display
Controller displays one more field to restart the reconstruction process.
This freeze mode is recommended only for frame-based pictures since
there is no motion between the fields.
When executing a Freeze Last Field, the Display Controller displays the
first field of the frame store once and then freezes on the last field of the
frame store. After the freeze condition is removed, the Display Controller
displays the last field one more time to restart the reconstruction
process. It then displays the first field of the next frame.
During Freeze First Field and Hold, the Display Controller only displays
the first field of the frame store. After the freeze is removed, the Display
Controller displays the first field once more to restart the reconstruction
process. It then displays the first field of the next frame.
Table 9.10
Freeze Modes
Freeze Mode Bits
Freeze Mode
0b00
Normal (no freeze)
0b01
Freeze Frame
0b10
Freeze Last Field
0b11
Freeze First Field and Hold