Configuration MC13xx
Users Manual Rev. 1.19
20
6.7 Clock
selection
The MC13xx is equipped with a 2-channel programmable clock synthesizer. One channel controls clock
frequency of the sensor (sensorclock, F
sens
), the other controls the frequency of the pixel clock (pixel-
clock, F
pix
). These independent clocks allow an always optimal ratio depending on the product of (im-
age size
•
image frequency) and the data rate on the output.
Example:
The MC13xx is connected to a frame grabber with a maximum data rate of 66MBytes/s via the„Base
Camera Link®“ interface using
2 x 8 bit video data.. A pixel clock of 33 MHz has to be selected.
As the sensor outputs 10 pixel per clock a sensor clock of 6.6MHz could be chosen. Because the sensor
can run up to a clock frequency of 66 MHz only 1/10 of the sensors possible speed would be used. To
make use of the maximum sensor clock and maintaining the maximum data rate on the output, just 120
(1280/10 rounded to steps of 10) from the possible 1280 pixel per line can be selected.
Therefore the ratio of F
sens
and F
pix
depends on the selected line length:
F
sens
<= (F
pix
•
1280) / (5 * line length)
or if 100 pixel line length is chosen:
F
sens
= (33
•
1280) / (5
•
100) = 70,4 MHz
As this exceeds the maximum sensor clock frequency, F
sens
is chosen as 66 MHz and F
pix
as 33 MHz.
6.7.1 Arbitrary selection of sensor and pixel clock
Sensor and pixel clock can be set to any value, the product of: (sensor clock
•
line length/1280) must
always be smaller (about 10%) than the qoutient: (pixel clock /
video data width
, e.g.: 2, or 8).
If
video data width
of 10 x 8-Bit is selected, sensor clock = pixel clock.
command
:S <x
0
>
<x
0
> ... 6 characters, as described in chapter
Frequency selection
6.7.2 Table selection of clock frequencies
To simplify clock selection when using video data width of 2, clocks can be selected from a table with
15 entries, each entry being optimized for four regions of line length. (see table in
9.3
).
Example:
240 < line length <= 640 Pixel, clock selection s9
pixelclock:
30,0
MHz
sensorclock:
11,2
MHz
resulting max. datarate on the 16-Bit output:
30,0 MHz/s * 2 Byte = 60,0 Mbyte/sec.