The AS8218 / AS8228 are highly integrated CMOS single-phase energy metering devices for fully electronic LCD meter systems. The AS8218 / AS8228 have been designed to ensure the meters full compliance with the international Standards IEC6052 and ANSI.

The AS8218 / AS8228 ICs include all the functions required for conventional 1- or 2-current anti-tamper meters. The functions include precision energy measurement, an 8-bit microcontroller unit (MCU), an on-chip Liquid Crystal Display driver (LCDD), programmable multipurpose Inputs/Outputs (MPIO), a real time clock/calendar (RTC) for complex tariff functions such as time-of-use or maximum demand billing and a Serial Peripheral Interface (SPI) for reading data from and writing data to an external non-volatile memory (EEPROM).

The AS8218 / AS8228 ICs have a dedicated energy measurement front-end, which includes an analog front-end and programmable Digital Signal Processor (DSP) from which active energy, mains voltage and mains current are provided. Reactive and apparent energy can also be calculated.

The on-chip 8-bit 8051 compatible microcontroller is freely programmable and provides user access to the various functional blocks. The dedicated Universal Asynchronous Receiver / Transmitter (UART1) in the System Control block provides access to various system functions and blocks. A second UART (UART2) is also provided, which may for example be used for debugging. The on-chip memory includes 24kByte program memory and 1kByte data memory. The meter system designer can select the size of the external EEPROM memory, from 1kByte to 32kByte (in binary steps).

An on-chip programmable watchdog timer (WDT) is available to automatically initiate a system reset if a regular ‘hold-off’ signal is not detected.

The system timing and real time clock (RTC) has a dedicated external battery supply pin (VDD_BAT), enabling the oscillator and RTC to continue during ‘power-down’. The RTC may be digitally calibrated for oscillator frequency accuracy.

The LCD Driver (LCDD) block enables the display of information provided by the microcontroller, directly to the LCD. 2 dedicated data register banks are provided to simplify programming, particularly in the case where the display data needs to be scrolled.

The programmable multi-purpose I/O pins (MPIO) may be independently configured as inputs or outputs. All the I/O pins are programmable for data direction, pull-up/pull-down resistors and drive strength (4mA/8mA). Typical functions may include LED energy consumption pulse output, energy direction and fault condition indication depending on current 1 or current 2 being active for the energy calculation, push button for display scrolling, mains isolation relay control for prepayment meters, optical interface, tamper detection etc.

An on-chip analog ground buffer (ABUF) and voltage reference (VREF) ensures that no external circuitry is required. A power-supply monitor (PSM) provides a reset, when VDD falls below a safe operating threshold. A reset pin (RES_N) is available for external system reset.

The AS8218 and AS8228 ICs are available in LQFP-64 plastic packages.