stv0903bab i2c-repeater question

stv0903bab i2c-repeater question

[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.

-- 
Sergey

Re: stv0903bab i2c-repeater question

[Andreas Regel]

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

Re: stv0903bab i2c-repeater question

[Sergey Mironov]

2010/3/31 Andreas Regel <andreas.regel@gmx.de>:
> 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