XE8806A SEMTECH [Semtech Corporation], XE8806A Datasheet - Page 106

• Manufacturer Part Number: XE8806A
• Description: Ultra Low-Power Low-Voltage
• Manufacturer: SEMTECH [Semtech Corporation]

14.12.2.5.3
To handle the transmission data by interrupt, enable the RF interface transmission interrupt in the interrupt handler
of the circuit.
We need to send the start sequence (preamble) first. The start sequence is defined as 10101010 10101010
10101010 11010100. Since the NRZ Level encoder is enabled, as “10101010”, “10101010”, “10101010” and
“11010100” should be written to the register RegRfifTx. The FIFO is now full, and we can wait for the interrupt
which will indicate that the FIFO is empty. At occurrence of the interrupt, 4 bytes of the message can be written to
the FIFO until all message bytes are sent.
14.12.2.6 Transmission mode using Manchester code
This RF link uses a transmission in the 433MHz frequency band. The protocol of the messages to be sent is
Manchester Space. The start sequence of the message is a code violation. The messages have a data rate of 19.2
kbit/s with a frequency deviation of 40 kHz. The output power is 15 dBm. The following paragraphs will show how
to set-up the XE1202A, how to set-up the RF interface and how to handle the received data.
14.12.2.6.1
To set the XE1202A in transmission mode, set the pins MODE(2:0) = 111.
To select the 433 MHz band, the bits FSParam_band = 01. The frequency deviation is set to 40 kHz by writing
RTParam_Dev = 10. The baud rate is set to 38.4 kb/s by writing FSParam_BR = 011. The output power is set to 15
dbm by writing RTParam_Tpow = 11. The setup of the XE1202A is shown in Table 14-33.
14.12.2.6.2
We then set-up the RF interface of the microcontroller circuit as a transmitter (RfifEnRx = 0 and RfifEnTx = 1).
Assume that the RC clock frequency used in the microcontroller is 1.2 MHz. To select the correct baud rate of 19.2
kbit/s according to the equation in chapter 14.10 (attention: the baud rate is twice the bit rate in the Manchester
code), fine*coarse=1.2e06/(16*38.4e3)=1.95. We can approximate this at 2. This can be done by setting
RfifBRCoarse = 00 and RfifBRFine = 0001.
The external bit synchronization clock is switched off by clearing the bit RfifTxClock = 0.
The encoder is enabled and set to Manchester Space encoding by setting RfifEnCod = 1 and RfifPCM = 010.
The set-up of the interface is summarized in Table 14-34.
© Semtech 2006
Register
RTParam1
RTParam2
FSParam1
FSParam2
FSParam3
DataOut
ADParam1
ADParam2
Pattern1
Pattern2
Pattern3
Pattern4
Table 14-33. XE1202A register set-up (see XE1202A datasheet for bit explanation)
Data transmission
XE1202A set-up
RF interface set-up
Register Address
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
14-26
0
0
0
0
0
0
0
0
0
0
0
0
7
0
1
1
0
0
0
0
0
0
0
0
0
6
0
0
0
0
0
0
0
0
0
0
0
0
5
0
0
1
0
0
0
0
0
0
0
0
0
4
0
0
1
0
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
2
XE8806A/XE8807A
1
0
1
0
0
0
0
0
0
0
0
0
1
1
0
1
0
0
0
0
0
0
0
0
0
0
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