MIL-STD-187-721D
c. The synchronous polling shall proceed through the channels from the initial channel to the next lower frequency, and so on, wrapping around from the lowest frequency to the highest, and continuing through all of the channels. Busy channels are not evaluated. Since both stations tune before the call, no tune time is needed between the call and the response. This permits additional speed-up in evaluating the channels. The stations always proceed to the next channel synchronously, whether or not they successfully measure the current channel (e.g., busy or non-propagating channels). The time step per channel is the longer tune time plus 18 Trw (redundant word time) (assuming three-character addresses).
d. The Type field of the channel scan request CMD word is set to 00 to distinguish it from other types of channel commands.
e. The Tune Time field is encoded as listed in table III. It indicates the time that must be allowed for tuning before each non-scanning call.
TABLE III. Tune time encoding.
f. The Mode field of the channel scan request CMD word is encoded as listed in table IV. The purpose of this field is to indicate whether data words follow the channel scan request CMD word, and whether they contain channel designators or frequency designators.
TABLE IV. Mode field encoding.
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