概述

　　早期水表多是采用干簧管、霍尔元件、韦根传感器组成。但由于干黄管受机械特性、使用寿命及抗震性影响大;霍尔元件存在低或高流速的频率响应问题;韦根传感器存在磁阻大的缺点，极易吸附住叶轮增加始动流量，且价格太贵。且这几种传感器都是带有磁特性的电子元件,在磁场作用下发出脉冲信息，因此，不可避免地会受到磁干扰。

　　无磁水表是通过在机表上安装一个随着水的流动而转动的圆盘，圆盘的一半镀上导电性能良好的金属，LC振荡电路的电感放于圆盘上方，通过采集LC振荡电路波形变化来计算水的流量，达到水表计量的目的。使用EFM32TG系列MCU设计的无磁水表可以很好的解决磁干扰问题，并且具有低功耗、低成本，电路设计简单等优点。

　　优势

　　· 基于Cortex-M3内核的低功耗芯片EFM32TG系列芯片具有以下优势：

　　低功耗：运行模式下功耗低至 150 μA/MHz;实时计数器运行、欠压和 RAM 与寄存器完全保持时电流消耗低至 1μA;具有100 nA接收模式的低能耗UART，超低功耗设计，延长电池使用寿命。

　　集成LCD 控制器：最多能够驱动8x20段LCD，满足各种水表显示需求。

　　集成LC传感器接口：低功耗传感器LESENSE接口可以直接测量LC传感器，高集成资源可以最大程度的减少无磁水表的外围器件，并且方便软件设计。

【EFM32TG】

EFM32TG Reference Manual

• 32-bit ARM Cortex-M3 processor running at up to 32 MHz

• Up to 32 kB Flash and 4 kB RAM memory

• Energy efficient and autonomous peripherals

• Ultra low power Energy Modes with sub-µA operation

• Fast wake-up time of only 2 µs

The EFM32TG microcontroller series revolutionizes the 8- to 32-bit market with acombination of unmatched performance and ultra low power consumption in bothactive- and sleep modes. EFM32TG devices consume as little as 150 µA/MHz in run mode, and as little as 1.0 µA with a Real Time Counter running, Brown-out and full RAM and register retention.

EFM32TG's low energy consumption outperforms any other available 8-, 16-, and 32-bit solution. The EFM32TG includes autonomous and energy efficient peripherals, high overall chip- and analog integration, and the performance of the industry standard 32-bit ARM Cortex-M3 processor.

Energy Friendly Microcontrollers

1.1 Typical Applications

The EFM32TG Tiny Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications. These devices are developed to minimize the energy consumption by lowering both the power and the active time, over all phases of MCU operation. This unique combination of ultra low energy consumption and the performance of the 32-bit ARM Cortex-M3 processor, help designers get more out of the available energy in a variety of applications.

Ultra low energy EFM32TG microcontrollers are perfect for:

• Gas metering

• Energy metering

• Water metering

• Smart metering

• Alarm and security systems

• Health and fitness applications

• Industrial and home automation

0 1 2 3 4

1.2 EFM32TG Development

Because EFM32TG use the Cortex-M3 CPU, embedded designers benefit from the largest development ecosystem in the industry, the ARM ecosystem. The development suite spans the whole design process and includes powerful debug tools, and some of the world’s top brand compilers. Libraries withdocumentation and user examples shorten time from idea to market.

The range of EFM32TG devices ensure easy migration and feature upgrade possibilities.

2 About This Document

This document contains reference material for the EFM32TG series of microcontrollers. All modules andperipherals in the EFM32TG series devices are described in general terms. Not all modules are present in all devices, and the feature set for each device might vary. Such differences, including pin-out, are covered in the device-specific datasheets.

2.1 Conventions

Register Names

Register names are given as a module name prefix followed by the short register name:

TIMERn_CTRL - Control Register

The "n" denotes the numeric instance for modules that might have more than one instance.

Some registers are grouped which leads to a group name following the module prefix:

GPIO_Px_DOUT - Port Data Out Register,

where x denotes the port instance (A,B,...).

Bit Fields

Registers contain one or more bit fields which can be 1 to 32 bits wide. Multi-bit fields are denoted with

(x:y), where x is the start bit and y is the end bit.

Address

The address for each register can be found by adding the base address of the module (found in the

Memory Map), and the offset address for the register (found in module Register Map).

Access Type

The register access types used in the register descriptions are explained in Table 2.1 (p. 3)

　　· 32.768KHz晶体(Q13FC1350000400)是超小型、薄、质地轻的表面贴片音叉型晶体谐振器，具备优良的耐热性，耐环境特性高精度晶振，加工方便且占用PCB面积小、受温度影响小，非常节约成本。

【Q13FC1350000400】

      【无磁水表】

　　无磁水表具有以下几大优势：

　　1、大量程比。运用电子跟踪补偿技术，量程比可达250比。

　　2、超长寿命。去除最易磨损、繁杂的齿轮计数部件，有效延长了流量计的运行稳定性和使用寿命。

　　3、智能平台。实现实时计量阶梯水价、M-BUS信息远传、大容量信息两地储存、远程水表运行状况自检、远程监测等多种功能。

　　4、可靠安全。采用远传光电隔离设计，支持带电无限次实时抄表。能有效抗击强磁、强电及雷电干扰。

　　5、高防护等级。采用电路盒内外等压技术，使水表达到IP67防护等级。

　　6、维护方便。电路盒和可以拆分式流量计，支持现场更换部件和电池。