Hello Sir/Madam,
In Apple Car Keys Specification R1 - Developer Preview 3 page 24, table 2-9, is mentioned the "NFC Protocol Start " parameter with the value of 5ms. Looks like this time was defined to include all the NFC procedures regarding protocol discovery and anti-collision, until the Select AID for the CCC applet command is issued.
Quote: "NFC protocol start includes all ISO 14443-3 commands required to setup the NFC communication (REQA, ATQA, AC, etc.).".
This requirement seems highly unfeasible on our side. The typical time on some of our products is between 30-50ms for the NFC protocol link set up. This includes the unmodulated carrier time, the VASUP command, REQA/ATQA sequence, HLTA/WUPA/ATQA sequence, ANTICOLLISION sequence, SELECT device ID/SAK/RATS/ATS sequence, all of which impossible to fit in 5ms even if we reduce everything to back to back communication and no delays between commands.
Can you further define what the "NFC Protocol Start " 5ms typical time means and how to interpret this time, for example:
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Can you enlist the starting point and ending point of measuring this 5ms time?
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Is this a strict requirement? What is the accepted time range if otherwise? (the document only mentions this is a "typical" time).
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Does this time also include the RF unmodulated field before the first NFC data transmission? (only this time can take up to 5ms according to ISSO-14443-3).
Thanks for your support!
Peter.