Silicon Laboratories SI4421 manual Si4421, FIFO and Reset Mode Command

Si4421

Bits 2-0 (f2 to f0): DQD threshold parameter.

The Data Quality Detector is a digital processing part of the radio, connected to the demodulator - it is an indicator reporting the reception of an FSK modulated RF signal. It will work every time the receiver is on. Setting this parameter defines how clean incoming data stream would be stated as good data (valid FSK signal).

If the internally calculated data quality value exceeds the DQD threshold parameter for five consecutive data bits for both the high and low periods, then the DQD signal goes high.

The DQD parameter in the Data Filter Command should be chosen according to the following rules:

The DQD parameter can be calculated with the following formula: DQDpar = 4 x (deviation – TX-RXoffset) / bit rate

It should be larger than 4 because otherwise noise might be treated as a valid FSK signal

The maximum value is 7.

7.FIFO and Reset Mode Command

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0	POR
	1	1	0	0	1	0	1	0	f3	f2	f1	f0	sp	al	ff	dr	CA80h

Bits 7-4 (f3 to f0):	FIFO IT level. The FIFO generates IT when the number of received data bits reaches this level.
Bit 3 (sp):	Select the length of the synchron pattern:
	sp	Byte1	Byte0 (POR)	Synchron Pattern (Byte1+Byte0)
	0	2Dh	D4h	2DD4h
	1	Not used	D4h	D4h

Note: The synchron pattern consists of one or two bytes depending on the sp bit. Byte1 is fixed 2Dh, Byte0 can be programmed by the Synchron Pattern Command (page 21).

Bit 2 (al):	Set the input of the FIFO fill start condition:
			al	FIFO fill start condition
		0			Synchron pattern
		1				Always fill

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