Texas Instruments TRF4903, Руководство пользователя, Страница: 18 / 26

www.ti.com
5.4 TRF4903 Registers
5.5 Transmit-Side Wireless Subroutines
Software Overview
Table 4. 6-Byte Transmission Data Packet
Header Byte Button 1 Button 2 Button 3 Button 4 Checksum Byte
OxFa ID Byte ID Byte ID BYte ID BYTe
5.3.3 Checksum Byte
Each packet has a checksum byte at the end of the data packet (see Table 4 ). The checksum byte is
calculated by summing the first 5 bytes of the packet and ignoring overflow.
The TRF4903 has five control registers (A through E) that are initialized using an on-chip serial port
interface (SPI).
Table 5 shows the values loaded into the registers by the microprocessor during demo
program initialization.
Table 5. TRF4903 Game Application Register Values
Register Parameter Value
A PA attenuation 0 dB
Mode 0 TX
Charge Pump 0.5 mA
Frequency Band 915 MHz
TX Frequency 902.3488 MHz
B PA attenuation 0 dB
PA Enabled
Mode 1 TX
Modulation FSK
Brownout threshold 2.2 V
Brownout detector On
TX Frequency 902.3488 MHz
C Reference divider 48
Reference frequency 409.6 kHz
D Crystal Tune 20.23 pF
Reset Signal for PFD Derived From Prescaler
Crystal Switch during OOK Open
E Transmit Capture Mode (TXM) High
Dividers D1 D2 D3 38.4 kbps
Terminal 16 Multiplex function Lock Detect
The game application uses a combination of C and MSP430 assembly language functions to implement
different communication tasks that are required to receive and send data. Brief descriptions of these
subroutines follow.
TRF4903 With MSP430 Demonstration and Development Evaluation Kit 18 SWRU010A – October 2004 – Revised May 2005