Hi All,
in yesterday’s AdHoc, when I presented the new suggested timing values for low speed Auto-Negotiation, I raised a question related to the original receive_DME_timer (this is the timer
specifying the maximum time to receive a complete AN page before going into timeout).
For the original high speed mode, this timer expires 6805 ns to 6925 ns after being started. The time can be calculated based on the page_test_max_timer + 2 * tdly of the
link segment + 5 ns
The minimum time is: 80 Bit * 60 ns (this is the time of a DME bit) + 2 * 1000 ns + 5 ns = 6805 ns
The maximum time is: 82 Bit * 60 ns (this is the time of a DME bit) + 2 * 1000 ns + 5 ns = 6925 ns
My question is now, where the additional 5 ns originally came from (at the moment I do not have this additional time in my timing calculations, as I do not see the reason for this
additional time). Nevertheless I do not want to remove the 5 ns in the LSM timing without knowing, what the original intent of adding this time was. If the 5 ns are needed to prevent some timer glitches or similar things, I will increase the receive_DME_timer
values for LSM AN, I suggested in yesterday’s presentation, by an additional 100 ns (scaling up the bit timing by a factor of 26.6666 would result in 133.333 ns, but if this is only a rough timing as it looks like, then 100 ns seem to be a good choice here,
if this additional time will be necessary).
So if you have some more information about this topic, then please let me know, so that if necessary, I can increase the receive_DME_timer value.
Thanks a lot.
Regards,
Steffen
Steffen Graber
Process Automation - Team Leader Business Unit Components+Technology
Fieldbus Technology
Pepperl+Fuchs GmbH
Lilienthalstrasse 200
68307 Mannheim
Germany
Phone: +49 621 776-1058
Fax: +49 621 776-1557
E-Mail:
sgraber@xxxxxxxxxxxxxxxxxxxx
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