XE8806A SEMTECH [Semtech Corporation], XE8806A Datasheet - Page 96

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

14.12.1.2.1
To set the XE1201A in reception mode, set the pin EN to 1 and the pin RXTX to 1. The data rate of the XE1201A
by default is 16kbit/s and the bit synchronizer is enabled by default. This means that the data registers of the
XE1201A can remain in the default settings shown in Table 14-20. The serial interface connections of Figure 14-8
are therefore not required.
14.12.1.2.2
Set-up the RF interface of the microcontroller circuit as a receiver (RfifEnRx = 1 and RfifEnTx = 0).
Assume that the RC clock frequency used in the microcontroller is 1.0 MHz. To select the correct baud rate of 16
kbit/s according to the equation in chapter 14.10, fine*coarse=1.0e06/(16*16e3)=3.9. This can be approximated at
4 (see specification in Table 14-19). This can be done by setting RfifBRCoarse = 01 and RfifBRFine = 0000.
The external bit synchronization clock is switched off by setting the bit RfifRxClock = 0.
The decoder is enabled and set to NRZ level decoding by setting RfifEnCod = 1 and RfifPCM = 000.
The start pattern detection is enabled by setting RfifEnStart = 11 and writing 11010111 to RfifRxSPat.
The start sequence detection interrupt is enabled by setting RfifRxIrqEn = 001.
The set-up of the interface is summarized in the Table 14-21.
14.12.1.2.3
In order to handle the received data by interrupt, enable the RF interface reception interrupt in the interrupt handler
of the circuit.
Data received before the first start pattern detection after the enabling of the interface are not relevant since we are
not yet synchronized to the messages. Since the start detection interrupt has been enabled, nothing has to be
done until the interrupt occurs.
When the first interrupt occurs, we are synchronized to the messages. In order to read data in an efficient way, the
interrupt source is modified and set to “Rx FIFO full” by writing 100 to RfifRxIrqEn. Once this is done, we can wait
for the next interrupt to download the received message.
At each new interrupt, we can now read 4 bytes of the received message by reading the register RegRfifRx 4
consecutive times. The interrupt should be served before the next byte is received since otherwise data may be
© Semtech 2006
Register
Register A
Register B
Register C
Table 14-20. XE1201A default register set-up (see XE1201A datasheet for bit explanation)
XE1201A set-up
RF interface set-up
Data reception
0
0
0
13
RegRfifRxSPat
0
0
1
12
RegRfifCmd1
RegRfifCmd2
RegRfifCmd3
Register
Table 14-21. RF interface set-up
0
0
0
11
0
0
1
10
0
0
0
9
14-16
0
0
1
8
0
0
0
7
0
0
0
6
00010000
11100000
00100010
11010111
contents
0
0
1
5
1
0
0
4
0
0
0
3
XE8806A/XE8807A
0
0
0
2
0
0
0
1
0
0
0
0
www.semtech.com