‡
Pre lim in a ry
MT9V012 - 1/6-In ch VGA CMOS Dig it a l Im a g e Se n so r
Fe a t u re De scrip t io n
Fra m e Ra t e Co n t ro l
For a given window size, the blanking registers (Reg0x05-Reg0x08), along with the row
speed register (Reg0x0A), can be used to set a particular frame rate.
The frame timing equations (Table 3 and Table 4 on page 12) can be rearranged to
express the horizontal blanking or vertical blanking values as a function of the frame
rate:
HBLANK_REG =
VBLANK_REG =
master clock freq / (frame rate * ((Reg0x03/S) + VBLANK_REG) * PIXCLK_PERIOD) - (Reg0x04/S)
master clock freq / (frame rate * ((Reg0x04/S) + HBLANK_REG) * PIXCLK_PERIOD) - (Reg0x03/S)
The HBLANK_REG value allows the frame rate to be adjusted with a minimum resolu-
tion of one PIXCLK_PERIOD multiplied by the total number of rows (displayed plus
blanking). If finer resolution is required, Reg0x0b (extra delay) can be used. Reg0x0b
allows the frame time to be changed in increments of 2 x (master clock period).
Min im u m Ho rizo n t a l Bla n kin g
The minimum horizontal blanking value is constrained by the time used for sampling a
row of pixels and the overhead in the row readout. This can be expressed in an equation
as:
HBLANK(MIN)
=
=
=
startup overhead + sampling time + extra cb time + dark col time
31+ done_sample/2 + 16 + 22 * read_dark_cols
47 + done_sample/2 + 22 * read_dark_cols
where:
done_sample
read_dark_cols
with default
settings:
=
=
Reg0x7E rounded up to nearest even number
Reg0x22, bit 8
HBLANK(MIN)
=
=
47+ (126)/2 + 22
132 PIXCLK periods
To get an aggressive minimum value for the horizontal blanking, the larger of
Reg0x79[15:8] and Reg0x76[15:8] can be substituted for the Reg0x7E value in the above
equation. With default settings, this gives a minimum HBLANK time of 127.
PDF: 814eb99f/Source: 8175e929
MT9V012_2.fm - Rev. B 2/05 EN
Micron Technology, Inc., reserves the right to change products or specifications without notice.
35
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