AS8267 datasheet(16/136 Pages) AMSCO

16 / 136 page

Data Sheet AS8267 / AS8268

Revision 1.0, 19-Jun-07

Page 16 of 136

A programmable watchdog timer is provided to automatically initiate a system reset when a regular hold-off

signal is not detected by the watchdog timer. The watchdog timer is an optional function which is software

enabled.

A dedicated serial Universal Asynchronous Receiver/Transmitter (UART1) Interface within the System Control

is provided to communicate with the AS8267 / AS8268 ICs and perform all the required programming and

reading of data, especially during the meter production process.

The AS8267 / AS8268 ICs supply voltages (2 x VDDD and VDDA) are typically 3.3 Volts. These supply

voltages should be derived from the Vmains with the use of a standard voltage regulated power supply circuit.

An on-chip power supply monitor (PSM) ensures that a reset is generated independently of the supply voltage

rise and fall times. Monitoring of the Vmains is provided to ensure early power-down detection. A reset pin

(RES_N) is also available for external system reset. The RES_N pin can be left unconnected if not required.

The individual functional elements of the AS8267 / AS8268 ICs, as well as the relationships between the

various functional blocks are shown in the following block diagram. A detailed description of the AS8267 /

AS8268 ICs system and the flexibility available to the kWh meter designer, through the system programmability

is also described below:

Analog

Front

End

DSP

TXD

RXD

VDD_BAT

XIN

XOUT

UART 1

MISO

MOSI

LBP3 ...0

LSD23 ...0

IO 11 ...0

S_N

I2N

I2P

I1N

I1P

Figure 2:

AS8267 / AS8268 block diagram

AS8267 Datasheet(PDF) 16 Page - ams AG