RFM22 Datasheet, PDF (31/150 Pages) –

RFM22
4.5. PN9 Mode
In this mode the TX Data is generated internally using a pseudorandom (PN9 sequence) bit generator. The primary
purpose of this mode is for use as a test mode to observe the modulated spectrum without having to load/provide
data.
4.6. Synchronous vs. Asynchronous
In Asynchronous mode no clock is used to synchronize the data to the internal modulator. This mode can only be
used with FSK. The advantage of this mode that it saves a microcontroller pin because no data clock is required.
The disadvantage is that you don‘t get the clean spectrum and limited BW of GFSK. If Asynchronous FSK is used
the TX_DR register should be set to its maximum value.
Figure 12. Direct Synchronous Mode Example
Figure 13. Direct Asynchronous Mode Example
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