On Wed, 24 Jun 2009, Fred wrote:
> Running on a TS-7200 but that doesn't really matter. What's amusing is
> that running a DOS program on a computer with a serial interface
> configured for 9600:O81 I can send message frames to the TS-7200 serial
Is the DOS program sending 7 data bits with the 8th bit odd parity?
If so, then I don't think I'm surprised. To the receiver all the 8 bits are
received as sent, but it just doesn't do any parity checking.
If it's sending 8 data bits and a 9th odd parity bit, then I'd expect
the receiving /dev/ttyAM0 to given errors on those words where the 9th bit
is not a "stop" bit.
What's the CRC that's computed and what is the exact data it is computed
on?
> interface /dev/ttyAM0 which is configured as 9600:N81 and despite the
> parity mismatch, the CRC appended to my inbound frame matches the
> TS-7200's computed CRC.
>
> The only thing I can think of is that when performing parity bit stuffing
> on one end and no bit elimination on the other, while the data in the
> received frame on the TS-7200 is wrong, the CRC match because the CRC is
> also bit shifted -- except that the CRC is a recursive polynomial so I
> would not have expected it to match.
>
> Kind of strange that a parity mismatch passes CRC checks some how.
>
> Unless I need coffee and missed something. }:-}
>
>
>
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