Re: stv0903bab i2c-repeater question

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2010/3/31 Andreas Regel <andreas.regel@xxxxxx>:
> Hi Sergey,
>
> Am 31.03.2010 12:14, schrieb Sergey Mironov:
>> Hello maillist!
>> I am integrating frontend with dvb-demux driver of one device
>> called mdemux.
>>
>> The frontend includes following parts:
>> - stv0903bab demodulator
>> - stv6110a tuner
>> - lnbp21 power supply controller
>>
>> stv6110a is connected to i2c bus via stv0903's repeater.
>>
>> My question is about setting up i2c repeater frequency divider (I2CRPT
>> register).  stv0903 datasheet says that "the speed of the i2c repeater
>> obtained by
>> dividing the internal chip frequency (that is, 135 MHz)"
>>
>> budget.c driver uses value STV090x_RPTLEVEL_16 for this divider. But
>> 135*10^6/16 is still too high to be valid i2c freq.
>>
>> Please explain where I'm wrong. Does the base frequency really equals to
>> 135
>> Mhz? Thanks.
>>
>
> The frequency divider in I2CRPT controls the speed of the I2C repeater HW
> unit inside the STV0903. The I2C clock itself has the same speed as the one
> that is used to access the STV0903. The repeater basically just routes the
> signals from one bus to the other and needs a higher internal frequency to
> do that properly. That is the frequency you set up with I2CRPT.
>
> Regards
> Andreas
>

Thanks, Andreas! Of cause, different i2c bus frequencies would require
some buffer inside repeater. But there is no information about such
things.
I've checked carefully and it seems that ENARPT_LEVEL actually defines
repeater delay.

-- 
Sergey
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