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EM250
4 Functional Description—System Modules
The EM250 contains a dual-thread mode of operation—System Mode and Application Mode—to guarantee
microcontroller bandwidth to the application developer and protect the developer from errant software
access.
During System Mode, all areas including the RF Transceiver, MAC, Packet Trace Interface, Sleep Timer, Power
Management Module, Watchdog Timer, and Power on Reset Module are accessible.
Since the EM250 comes with a license to EmberZNet PRO, the Silicon Labs ZigBee-compliant software stack,
these areas are not available to the application developer in Application Mode. The following brief description
of these modules provides the necessary background on the operation of the EM250. For more information,
contact support at www.silabs.com/zigbee-support .
4.1
Receive (RX) Path
The EM250 RX path spans the analog and digital domains. The RX architecture is based on a low-IF, super-
heterodyne receiver. It utilizes differential signal paths to minimize noise interference. The input RF signal is
mixed down to the IF frequency of 4MHz by I and Q mixers. The output of the mixers is filtered and combined
prior to being sampled by a 12Msps ADC. The RX filtering within the RX path has been designed to optimize the
co-existence of the EM250 with other 2.4GHz transceivers, such as the IEEE 802.11g and Bluetooth.
4.1.1
RX Baseband
The EM250 RX baseband (within the digital domain) implements a coherent demodulator for optimal
performance. The baseband demodulates the O-QPSK signal at the chip level and synchronizes with the IEEE
802.15.4-2003 preamble. An automatic gain control (AGC) module adjusts the analog IF gain continuously
(every ? symbol) until the preamble is detected. Once the packet preamble is detected, the IF gain is fixed
during the packet reception. The baseband de-spreads the demodulated data into 4-bit symbols. These
symbols are buffered and passed to the hardware-based MAC module for filtering.
In addition, the RX baseband provides the calibration and control interface to the analog RX modules,
including the LNA, RX Baseband Filter, and modulation modules. The EmberZNet PRO software includes
calibration algorithms which use this interface to reduce the effects of process and temperature variation.
4.1.2
RSSI and CCA
The EM250 calculates the RSSI over an 8-symbol period as well as at the end of a received packet. It utilizes
the RX gain settings and the output level of the ADC within its algorithm. The linear range of RSSI is specified
to be 40dB over all temperatures. At room temperature, the linear range is approximately 60dB (-90 dBm to -
30dBm).
The EM250 RX baseband provides support for the IEEE 802.15.4-2003 required CCA methods summarized in
Table 10. Modes 1, 2, and 3 are defined by the 802.15.4-2003 standard; Mode 0 is a proprietary mode.
Page 17
120-0082-000V Rev 1.1
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相关代理商/技术参数
EM250-COMP-XIDE 制造商:Silicon Laboratories Inc 功能描述:COMPILER XIDE FOR EM250 1SEAT
EM250-DEV 功能描述:KIT DEV FOR EM250 RoHS:否 类别:RF/IF 和 RFID >> RF 评估和开发套件，板 系列:InSight 标准包装:1 系列:- 类型:GPS 接收器 频率:1575MHz 适用于相关产品:- 已供物品:模块 其它名称:SER3796
EM250-EK-R 功能描述:KIT EVAL EM250 RF TEST RoHS:是 类别:RF/IF 和 RFID >> 过时/停产零件编号 系列:InSight 标准包装:1 系列:- 类型:用于 200/300 系列的欧盟开发套件 适用于相关产品:Zensys RF 模块 所含物品:开发板，模块，编程器，软件，线缆，电源 其它名称:703-1019Q3225667
EM250-JMP-R 功能描述:KIT JUMP START FOR EM250 RoHS:否 类别:RF/IF 和 RFID >> RF 评估和开发套件，板 系列:JumpStart 标准包装:1 系列:- 类型:GPS 接收器 频率:1575MHz 适用于相关产品:- 已供物品:模块 其它名称:SER3796
EM250-RCM-R 功能描述:EM250 RCM BOARD RoHS:是 类别:RF/IF 和 RFID >> RF 评估和开发套件，板 系列:- 标准包装:1 系列:- 类型:GPS 接收器 频率:1575MHz 适用于相关产品:- 已供物品:模块 其它名称:SER3796
EM250-RTR 功能描述:IC ZIGBEE SYSTEM-ON-CHIP 48-QFN RoHS:是 类别:RF/IF 和 RFID >> RF 收发器 系列:EM250 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:30 系列:- 频率:4.9GHz ~ 5.9GHz 数据传输率 - 最大:54Mbps 调制或协议:* 应用:* 功率 - 输出:-3dBm 灵敏度:- 电源电压:2.7 V ~ 3.6 V 电流 - 接收:* 电流 - 传输:* 数据接口:PCB，表面贴装 存储容量:- 天线连接器:PCB，表面贴装 工作温度:-25°C ~ 85°C 封装/外壳:68-TQFN 裸露焊盘 包装:管件
EM250-STACK-R 制造商:Silicon Laboratories Inc 功能描述:EM250 BOARD STACK (RCM + BREAKOUT) - Boxed Product (Development Kits) 制造商:Silicon Laboratories Inc 功能描述:BOARD STACK EM250 RCM & BREAKOUT
EM25-12V-DC 制造商:ECLIPSE MAGNETICS 功能描述:HOLDING ELECTRO MAGNET