FXTH870xD
Sensors
Freescale Semiconductor, Inc.
119
Figure 96. Bi-Phase Data Bit Encoding (POL = 0)
Figure 97. Bi-Phase Data Bit Encoding (POL = 1)
13.6
RF Output Stage
The RF output stage consists of a PLL, control logic and an output RF amplifier. Data is sent to the RF output stage from either
the RF data buffer or the DATA bit in the RFCR3 depending on the selected mode of operation as described in
The RF output stage is enabled by the state of the SEND control bit. The PLL in the RF output stage will signal back via the RCTS
status bit when the PLL is locked and ready to transmit.
13.6.1
Modulation Method
The modulation control bit, MOD, described in
,
sets the modulation of the RF signal will be either amplitude shift
keying (OOK) or frequency shift keying (FSK) with several options for the frequency shift.
When operating in the FSK mode the internal, fractional-n PLL divider will be used to create the two carrier frequencies for data
zero and data one. This method is more effective and robust than “pulling” the external crystal in order to shift the carrier
frequency.
LOW
BIT
HIGH
BIT
Bit Time
Consecutive “0”
Data Bits
Consecutive “1”
Data Bits
LOW
BIT
“001101”
Data Bits
HIGH
BIT
FSK = f
RF
+
f
FSK = f
RF
-
f
OOK = f
RF
OOK = OFF
Bit Time
Bit Time
Bit Time
OOK = f
RF
LOW
BIT
HIGH
BIT
Bit Time
Consecutive “0”
Data Bits
Consecutive “1”
Data Bits
LOW
BIT
“001101”
Data Bits
HIGH
BIT
FSK = f
RF
+
f
FSK = f
RF
-
f
OOK = OFF
Bit Time
Bit Time
Bit Time
Содержание FXTH870 D Series
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