[linux-dvb] Possible patch for CAM/CI issues

Georg Acher acher at in.tum.de
Mon Nov 7 19:08:13 CET 2005


On Mon, Nov 07, 2005 at 07:41:50PM +0200, irk wrote:
> I can add this symptom:
> 
> I have two CAM's, one is called Matrix Revolutions, another is called X-CAM.
> These are CAM's which can be used with multiple encryption systems. I tested
> them with SECA Mediaguard. What happens is that X-CAM works perfectly but
> Matrix has big troubles. Lots of squares appear in the picture and driver 
> complains
> about CRC errors. Both CAM's work perfectly in quite old set-top box.

The signal integrity of some CAMs is quite bad. The have slow and and
irregular rise and fall times for the clock, with varying setup/hold times
for the data. This can lead to data corruption on the receiving side of the
CI slot. AFAIK the Matrix cam was one of the worst I've seen. I can't
imagine how one create such an "analog" clock signal from a digital
source...

Other CAMs (eg. Dragon Twin) have a bug in the PCMCIA bus interface and
ignore the slot specific CE1 and use only OE/WE for decoding. If you have
two slots with shared OE/WE (which is quite normal, eg. the FF cards with
the CI slot extension), only one CAM works. A second CAM (no matter which
type) is not correctly detected due to bus collisions.

In short: There is so much badly designed crap in the CAM market. It is
a wonder that at least some CAM/receiver combinations work...

-- 
         Georg Acher, acher at in.tum.de
         http://www.lrr.in.tum.de/~acher
         "Oh no, not again !" The bowl of petunias



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