NXP 公司的EM773是基于ARM Cortex-M0的低功耗32位智能电表集成电路，CPU频率高达48MHz，具有丰富外设包括多达32KB标闪存，多达8KB数据存储器，一个Fast-mode PlusI2C总线接口，一个RS-485/EIA-485 UART，一个带SSP特性的SPI接口，三个通用计数器/定时器，多达25个GPIO，以及用于电能测量的测量引擎。本文介绍了EM773主要特性和优势，方框图，智能电表原理方框图，电表主要元件BOM以及智能电表无线插头电表电路图和电表指标。

EM773：Energy metering IC; up to 32 kB flash and 8 kB SRAM

The EM773 is an ARM Cortex-M0 based， low-cost 32-bit energy metering IC， designed for 8/16-bit smart metering applications. The EM773 offers programmability and on-chip metrology functionality combined with a low power， simple instruction set and memory addressing with reduced code size compared to existing 8/16-bit architectures.

The EM773 operates at CPU frequencies of up to 48 MHz.

The peripheral complement of the EM773 includes up to 32 kB of flash memory， up to 8 kB of data memory， one Fast-mode Plus I2C-bus interface， one RS-485/EIA-485 UART，one SPI interface with SSP features， three general purpose counter/timers， up to 25 general purpose I/O pins， and a metrology engine for energy measurement.

EM773主要特性和优势：

System:
ARM Cortex-M0 processor， running at frequencies of up to 48 MHz.
ARM Cortex-M0 built-in Nested Vectored Interrupt Controller (NVIC).
Serial Wire Debug.
System tick timer.

Memory:
32 kB on-chip flash programming memory.
8 kB SRAM.
In-System Programming (ISP) and In-Application Programming (IAP) via on-chip bootloader software.

Digital peripherals:
Up to 25 General Purpose I/O (GPIO) pins with configurable pull-up/pull-down resistors.
GPIO pins can be used as edge and level sensitive interrupt sources.
High-current output driver (20 mA) on one pin.
High-current sink drivers (20 mA) on two I2C-bus pins in Fast-mode Plus.
Three general purpose counter/timers with a total of two capture inputs and 10 match outputs.
Programmable WatchDog Timer (WDT).

Analog peripherals:
Metrology Engine for Smart Metering with two current inputs and a voltage input.

Serial interfaces:
UART with fractional baud rate generation， internal FIFO， and RS-485 support.
One SPI controller with SSP features and with FIFO and multi-protocol capabilities.
I2C-bus interface supporting full I2C-bus specification and Fast-mode Plus with a data rate of 1 Mbit/s with multiple address recognition and monitor mode.

Clock generation:
12 MHz internal RC oscillator trimmed to 1 % accuracy that can optionally be used as a system clock.
Crystal oscillator with an operating range of 1 MHz to 25 MHz.
Programmable watchdog oscillator with a frequency range of 7.8 kHz to 1.8 MHz.
PLL allows CPU operation up to the maximum CPU rate without the need for a high-frequency crystal. May be run from the system oscillator or the internal RC oscillator.
Clock output function with divider that can reflect the system oscillator clock， IRC clock， CPU clock， and the Watchdog clock.

Power control:
Integrated PMU (Power Management Unit) to minimize power consumption during Sleep， Deep-sleep， and Deep power-down modes.
Three reduced power modes: Sleep， Deep-sleep， and Deep power-down.
Processor wake-up from Deep-sleep mode via a dedicated start logic using up to 13 of the functional pins.

Power-On Reset (POR).
Brownout detect with four separate thresholds for interrupt and forced reset.
Unique device serial number for identification.
Single 3.3 V power supply (1.8 V to 3.6 V).
Available as 33-pin HVQFN package.

EM773应用：
Smart Metering

 
图1。EM773方框图

 
图2。EM773智能电表原理方框图

 
图3。EM773 CGU方框图

 
 
图5。EM773插头式电表外形图

 
图6。EM773智能电表无线插头电表电路图