[aprssig] AX.25 'H' flag
bruninga at usna.edu
Mon Nov 14 10:50:32 CST 2005
THe AEA's use a non-TAPR-2 monitor mode
display standard and they DO show the * for
every digi. But the TAPR standard only shows
them on the LAST digi heard. Bob
>>> aprs at kd4rdb.com 11/14/05 11:19 AM >>>
I am indeed talking about the kiss/ax.25 spec... I used the CONV mode
method of H bit indication... so a little mixing of terms here... but I
did see a difference in the way the kpc3's and pacomms dealt with H bits.
I think Bob said it would be chaotic... and he's right... but it's what
I saw. Unfortunately, I don't remember which TNC filled up the h bits,
and which on just set the current bit.
Curt, WE7U wrote:
> On Mon, 14 Nov 2005, Wes Johnston wrote:
>>passing thru a mishmash of digipeaters, you can end up with a packet
>>In either of these cases, digi4 should figure out that it's the one
>>supposed to digi next... This point drove me nuts when I wrote my kiss
>>digipeater years ago. Best to parse packet paths from the END and work
>>toward the first path element looking for any H flag to be set. This
>>also plays well with pre-emptive digipeating.
> Wes, if you're really talking KISS packets (or raw AX.25 packets)
> then you should never see the operation you describe else it's a bug
> in the software in those TNC's and not per spec. That bit _must_
> get set in order to show that the slot is used up. Havoc will reign
> For command-mode TNC's then the '*' really can't be relied upon to
> indicate state of each digipeater field. The most common format
> would be a single asterisk at the last used-up digipeater slot. The
> other format I know of would be an asterisk for every one from the
> beginning to the last used-up slot, which is more indicative of the
> state of the bit for each slot than the first format.
> Curt, WE7U. APRS Client Comparisons: http://www.eskimo.com/~archer
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