ov9625 ETC-unknow, ov9625 Datasheet - Page 7

• Manufacturer Part Number: ov9625
• Description: Ov9625 Color Cmos Sxga Mpixel Camerachip Ov9121 Cmos Sxga Mpixel Camerachip
• Manufacturer: ETC-unknow

O
Timing Generator
Version 1.3, September 15, 2003
mni
In general, the timing generator controls the following
functions:
•
•
•
Frame Exposure Mode Timing
OV9625/OV9121
Typically the frame exposure mode must work with the aid
of an external shutter.
The frame exposure pin,
exposure mode enable pin and
as the exposure start trigger for the sensor. There are two
ways to set Frame Exposure mode:
•
•
When the external master device asserts the
high, the sensor array is quickly pre-charged and stays in
reset mode until the
external master (sensor exposure time can be defined as
the period between
the
clocked to the output port in a line-by-line manner. After
completing one frame of data output, OV9625/OV9121
will output continuous live video data unless in single
frame transfer mode.
detailed timing for this mode.
For frame exposure, register
0xFF and register
0x10 (maximum 2x gain).
FREX
Frame Exposure Mode Timing
Frame Rate Timing
Frame Rate Adjust
Control both
Exposure mode can be set by pulling both FREX and
EXPSTB pins high at the same time (see
Control
case, the pre-charge time is tline and sensor
exposure time is the period after pre-charge until the
shutter closes (see
ision
pin is pulled low, the video data stream is then
FREX
FREX
only and keep
GAIN
supports
EXPSTB
EXPSTB
Figure 18
and
Figure
(0x00) should be no larger than
FREX
EXPSTB
AEC
low to shutter close). After
frame
18).
EXPSTB
pin is pulled low by the
and
EXPSTB
(0x10) must be set to
(pin 8) is the frame
Figure 19
pins - Frame
exposure
(pin 12) serves
low - In this
Figure
FREX
show the
mode.
19).
pin
Proprietary to OmniVision Technologies
PCLK (MHz)
NOTE: Based on 24 MHz external clock and internal PLL
on, frame rate is adjusted by the main clock divide method.
Frame Rage (fps)
Frame Rate Timing
Default frame timing is illustrated in
Figure
different frame rates.
Table 2
Frame Rate Adjust
OV9625/OV9121 offers three methods of frame rate
adjustment.
1.
2.
3.
After changing registers
to adjust the dummy pixels, it is necessary to write to
register
counter. Generally, OmniVision suggests users write to
register
last one. However, if you want to adjust the cropping
window, it is necessary to write to those registers after
changing register
the counter, it is necessary to generate a pulse on
resolution control register bit COMH[6].
Clock prescaler (see
By changing the system clock divide ratio, the frame
rate and pixel rate will change together. This
method can be used for dividing the frame/pixel rate
by: 1/2, 1/3, 1/4 … 1/64 of the input clock rate.
Line adjustment (see
“FRARL” on page
By adding dummy pixel timing in each line, the
frame rate can be changed while leaving the pixel
rate as is.
Vertical sync adjustment
By adding dummy line periods to the vertical sync
period (see
“ADDVSH” on page
altered while the pixel rate remains the same.
17. Refer to
COMH
COMH
Frame and Pixel Rates
(0x12) (to change the sensor mode) as the
(0x12) or
“ADDVSL” on page 25
COMH
Table 2
15
24
25)
COML
25), the frame rate can be
(0x12). To use
“CLKRC” on page
“COML” on page 24
CLKRC
10
16
for the actual pixel rate at
(0x2A) and
Functional Description
7.5
12
(0x11) to reset the
and see
COMH
Figure 16
FRARL
9.6
6
20)
and see
to reset
(0x2B)
5
8
and
7