Revision 2.1, 06-Oct-05
Page 1 of 2
1. Key Features
-
Precision single-phase, one or two current input
energy measurement front-end including Sigma-
Delta modulators for A/D-conversion and digital
signal processor (DSP).
-
Low current consumption of 5mA, depending on
MCU activity.
-
Digital phase correction and selectable gain on
both current channels for use with two current
transformers (CT) or one CT and one shunt.
-
Power-supply monitor (PSM) for power-on reset
and reset when the supply voltage falls below a
defined threshold.
-
Customer programmable 8-bit 8051 compatible
microcontroller (MCU).
-
Programmable MCU clock with optional low
power operating conditions.
-
2 x Universal Asynchronous Receiver /
Transmitters (UART) for external
communications such as programme download
and debugging.
-
Real-time clock/calendar (RTC) with on-chip
digital calibration and separate battery backup
pin.
-
On-chip voltage reference (VREF) with small
temperature coefficient.
-
Low power 3.0 4.0MHz crystal oscillator.
-
SPI compatible interface for external EEPROM
memory.
-
Standard on-chip LCD driver (LCDD) interface.
-
Programmable multi-purpose I/Os (MPIO) with
selectable data direction, pull-up or pull-down
resistors and drive strength.
-
Low power battery operating mode for meter
reading when Mains voltage is not present.
-
The difference between the AS8218 and
AS8228 ICs are:
AS8218: 20 x 4 segment LCDD
9 x multi-purpose I/O (MPIO)
AS8228: 24 x 4 segment LCDD
12 x multi-purpose I/O (MPIO)
2. General Description
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 that meters
can fully comply with the international Standards
IEC1036 and ANSI.
The AS8218 / AS8228 ICs include all the functions
required for conventional 1 current 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 and selectable multi-
purpose 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 include 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.
Due to the large diversity of non-volatile memory
requirements for fully electronic single-phase
metering systems, the AS8218 / AS8228 ICs allow
the system designer to select the size of the
external EEPROM memory, 1kByte to 32kByte (in
binary steps).
The system timing and real time clock (RTC) has a
dedicated supply pin (VDD_BAT), which is separate
from the rest of the IC, enabling the oscillator to be
supplied with an external battery during `power-
AS8218 / AS8228
Highly Integrated Single Phase 2-Current Energy
Metering Integrated Circuits with Microcontroller, RTC,
Programmable Multi-Purpose I/Os and LCD Driver
FEATURES
Features AS8218 / AS8228
Revision 2.1, 06-Oct-05
Page 2 of 2
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.
Two 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 dedicated
inputs or outputs. All the I/O pins are
programmable for data direction, pull-up/pull-down
resistors and drive strength (4mA/8mA). Such
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 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.
The AS8218 / AS8228 ICs are available in a
LQFP64 plastic package.
3. AS8218 / AS8228 Block Diagram
System Timing &
Real Time Clock
Energy Measurement
Front End
System
Control
8051
Micro-
Controller
LCD
Driver
Multi-purpose
I/Os
SPI
Analog
Front
End
DSP
LBP3 ... 0
SC
IO11 ... 0
LSD23 ... 0
TXD
SI
SO
S_N
RXD
I2N
I2P
I1N
I1P
VN
VP
VDD_BAT
XIN
XOUT
UART1
Figure 1:
AS8218 / AS8228 block diagram
4. Contact
austriamicrosystems AG
A 8141 Schloss Premstaetten, Austria
T. +43 3136 500 0
F. +43 3136 525 01
info@austriamicrosystems.com
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