How to configure the OSCIN settings for 25 Mhz crystal

Boris Fennema

Other Parts Discussed in Thread: OMAP-L138

Dear all,

We have a board and firmware laid out for 300 Mhz CPU speed, with a 24 MHz OSCIN crystal.

We would like to experiment with a different crystal which is 25 Mhz. I have read spruh77 but am somewhat confused still.

Is it possible to use a 25 Mhz crystal as external oscilator and tweak the settings for the clock rate.

Table 7-5 does not mention a 25 MHz OSCIN rate for DDR2 speed for example.

Somewhat lost !

over 11 years ago

0 Antony Samsunil over 11 years ago

TI__Expert 4760 points

Hi Boris,

The maximum OSCIN frequency supported by OMAP-L138 device is 50 MHz .You can use 25MHz OSCIN and tweak the settings for the clock rate.

The example is given for 24MHz OSCIN frequency that does not mean you need to use 24MHz only, you can try different OSCIN frequency supported by the device’s minimum and maximum frequency ranges.

That too DDR2 controller is sourced by separate PLL1 controller instead of PLL0 for CPU.

Please check the Clocking spread sheet tools for OMAP-L138 for more details on programming the systems and peripheral clock.

http://processors.wiki.ti.com/index.php/File:SYS_CLK_CALC_OMAP-L138_C674X_AM18X_v1p0.zip

Regards

Antony

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0 Boris Fennema over 11 years ago in reply to Antony Samsunil

Intellectual 510 points

Thanks - that explains it well.

Many thanks.

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How to configure the OSCIN settings for 25 Mhz crystal