> -----Original Message----- > From: Issa Gorissen [mailto:flop.m@xxxxxxx] > Sent: lundi 3 octobre 2011 15:18 > To: o.endriss@xxxxxx; Sébastien RAILLARD > Cc: Linux Media Mailing List > Subject: Re: [DVB] CXD2099 - Question about the CAM clock > > > Dear Oliver, > > > > I?ve done some tests with the CAM reader from Digital Devices based on > Sony > > CXD2099 chip and I noticed some issues with some CAM: > > * SMIT CAM : working fine > > * ASTON CAM : working fine, except that it's crashing quite > regularly > > * NEOTION CAM : no stream going out but access to the CAM menu is ok > > > > When looking at the CXD2099 driver code, I noticed the CAM clock > > (fMCLKI) > is > > fixed at 9MHz using the 27MHz onboard oscillator and using the integer > > divider set to 3 (as MCLKI_FREQ=2). > > > > I was wondering if some CAM were not able to work correctly at such > > high clock frequency. > > > > So, I've tried to enable the NCO (numeric controlled oscillator) in > > order > to > > setup a lower frequency for the CAM clock, but I wasn't successful, > > it's looking like the frequency must be around the 9MHz or I can't get > > any stream. > > > > Do you know a way to decrease this CAM clock frequency to do some > testing? > > > > Best regards, > > Sebastien. > > Weird that the frequency would pose a problem for those CAMs. The CI > spec [1] explains that the minimum byte transfer clock period must be > 111ns. This gives us a frequency of ~9MHz. > You're totally right about the maximum clock frequency specified in the norm, but I had confirmation from CAM manufacturers that their CAM may not work correctly up to this maximum frequency. Usually, the CAM clock is coming from the input TS stream and I don't think there is for now a DVB-S2 transponder having a 72mbps bitrate (so a 9MHz for parallel CAM clocking). > Anyway, wouldn't it be wiser to base MCLKI on TICLK ? > I've tried to use mode C instead of mode D, and I have the same problem, so I guess TICLK is around 72MHz. It could be a good idea to use TICLK, but I don't know the value and if the clock is constant or only active during data transmission. Did you manage to enable and use the NCO of the CXD2099 (instead of the integer divider) ? > -- > Issa > > [1] http://www.dvb.org/technology/standards/En50221.V1.pdf -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
