Oliver Neukum wrote:
Am Samstag, 9. Dezember 2006 07:11 schrieb Ben Nizette:
Also, you mentioned that the corruption occurs systematically on certain
byte patterns. Therefore it's certainly not related to the cables.
It'd guess that too, but who can that say for sure. :-|
You may have a bit pattern that stresses the controllers and suddenly
a marginal cable may matter.
The errors occur in strings of 0xFFs. From the USB standard:
a “1” is represented by no change in level and a “0” is represented by a
change in level
Yes, plus added stuffing bits.
so this error-infested bytes are effectively long, quiet times on the
wire. I would have thought this would be the _least_ stressful time for
the controllers but maybe they are also more susceptible to noise during
this period.
The longer you don't change the voltage the likelier are reciever and
transmitter to get out of sync.
Yes, hence the bit-stuffing, you're right :). And hence this period
isn't really too stressful for the controller as the stuffed bits come
relatively often.
We're hoping that any wire-errors get picked up by the CRC anyway so a
marginal cable under any circumstances shouldn't silently corrupt data.
I love that word 'shouldn't' ;)
Regards,
Ben.
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