AS8218 datasheet(98/123 Pages) AMSCO

98 / 123 page

Data Sheet AS8218 / AS8228

Revision 3.0, 31-May-06

Page 98 of 123

8.7

System Control (SCT)

The system control is responsible for handling different modes of operation such as normal mode (metering

functions) and test mode.

The clock generation and reset control are also available in System Control (SCT).

Modes of Operation

Power off

In this mode everything is off including the ‘System Timing and RTC’ block, provided that no battery is

connected to VDD_BAT or the battery is discharged. Nothing happens.

RTC on, Rest of the Chip off

In this mode the ‘System Timing and RTC’ block is supplied by a battery, the RTC is working, but no interrupts

are generated.

At the moment the battery is inserted, a power-on reset just for the RTC will be generated. The reset will be set

to 0 after the first clock edges arrive.

Power-up Phase

When the power is switched on (for the ‘rest’ of the chip), there is a power-on reset first and the reset is held

until the BOOTLOAD block has finished operation. The BOOTLOAD block will load the P_RAM from the

external EEPROM.

After BOOTLOAD the MCU will start to work. The loaded program will be executed. It is assumed that at the

beginning of the program various system parameters are set (sel_i, sel_v, sel_p, creep etc.)

No EEPROM programmed, must be loaded from outside

If the EEPROM does not contain a program the MCU will run idle mode. It is necessary to write a program to

the EEPROM next.

Write to EEPROM

The EEPROM can directly be written (from outside) using the UART1 interface. The following diagram shows

the main blocks involved:

UART1

SCT

SPI

EEPROM

RXD

S_N

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