XE8000EV108 Semtech, XE8000EV108 Datasheet - Page 102

• Manufacturer Part Number: XE8000EV108
• Description: EVAL BOARD FOR XE8806/XE8807
• Manufacturer: Semtech
• Type: MCUr

Specifications of XE8000EV108

• Contents: Fully Assembled Evaluation Board
• For Use With/related Products: XE88LC06AMI026
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

The first example below (chapter 14.12.2.3) uses the XE1202A clock. In the other examples, the internal RC clock
is used.
14.12.2.3 Reception mode using NRZ coding and the XE1202A bit and message synchronizer
This RF link uses a wide band transmission in the 915MHz frequency band. The protocol of the messages
received is NRZ Mark. The start sequence of the message is a 4 byte pattern (10101010 10101010 10101010
11010100). The received messages have a data rate of 76.8 kbit/s with a frequency deviation of 100 kHz. 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. The microcontroller derives its clock from the XE1202A.
14.12.2.3.1
To set the XE1202A in reception mode, set the pins MODE(2:0) = 100.
To select the 915MHz band, the bits FSParam_band = 11. The bandwidth of the baseband filter is set to 200 kHz
by writing RTParam_BW = 11. The bit rate is set to 76.8 kbit/s by writing FSParam_BR = 100. The bit synchronizer
is enabled (RTParam_bits = 1). The pattern recognition is enabled (ADParam_Pattern =1) and the length of the
pattern is set to 32 bit (ADParam_Psize = 11). The pattern is written to the 4 pattern registers. The output clock is
enabled (RTParam_Clkout = 1) and its frequency is set to 2.44 MHz (ADParam_Clkfreq = 01).
Table 14-27. XE1202 register set-up (see XE1202 datasheet for bit explanation)
14.12.2.3.2
We then set-up the RF interface of the microcontroller circuit as a receiver (RfifEnRx = 1 and RfifEnTx = 0).
The external clock frequency generated by the XE1202A is 2.44 MHz. The external clock source has to be
selected by writing SelExtClock = 1 in RegSysClock. The frequency used in the microcontroller is half of this (see
clock block documentation): 1.22 MHz. To select the correct baud rate of 76.8 kbit/s according to the equation in
chapter 14.10, fine*coarse=1.22e06/(16*76.8e3)=0.99. We can approximate this at 1 (see specification in Table
14-19). This can be done by setting RfifBRCoarse = 00 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 Mark decoding by setting RfifEnCod = 1 and RfifPCM = 001.
The external start pattern detection is enabled by setting RfifEnStart = 10.
The start sequence detection interrupt is enabled by setting RfifRxIrqEn = 001.
The set-up of the interface is summarized in the Table 14-28.
© Semtech 2006
Register
RTParam1
RTParam2
FSParam1
FSParam2
FSParam3
DataOut
ADParam1
ADParam2
Pattern1
Pattern2
Pattern3
Pattern4
XE1202A set-up
RF interface set-up
Register Address
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
14-22
0
0
1
0
0
0
1
0
1
1
1
1
7
1
1
1
0
0
0
1
0
0
0
0
1
6
0
0
1
0
0
1
0
0
1
1
1
0
5
0
0
0
0
0
0
0
0
0
0
0
1
4
1
0
0
0
0
0
0
0
1
1
1
0
3
1
0
1
0
0
0
0
0
0
0
0
1
2
XE8806A/XE8807A
0
0
0
0
0
0
1
0
1
1
1
0
1
0
1
0
0
0
0
0
0
0
0
0
0
0
www.semtech.com