backward compatibility
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S3[6-7] Interval. This field specifies the interval, in
multiples of 21.22 milliseconds. (For backward
compatibility only. New applications should use 3.
Use of this field to specify an interval is being
phased out.)
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... the time interval over which the <data words per
interval> data in <max mes> messages will be sent. For
backward compatibility, an interval of 0 selects an
interval of 169.76 milliseconds. This field is ignored
unless the INT field is 3.
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... 0[5-7] HAP version number. Use 1. Use of zero invokes
backward compatibility code (see Appendix B).
0[8-11] Reserved. Must be zero.
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... 0[5-7] HAP version number. Use 1. Use of zero invokes
backward compatibility code (see Appendix B).
0[8-9] Reserved. Must be zero.
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... Appendix B -- Backward compatibility ...