ATM90E32AS-AU-R datasheet(12/84 Pages) ATMEL

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M90E32AS [Datasheet]

Atmel-46003B-SE-M90E32AS-Datasheet_02122015

3.5

METERING FUNCTION

Metering is enabled when any of the MeterEn bits are set.

When metering is not enabled, the CF pulse will not be generated and energy accumulator will not accumulate energy. All

energy accumulation related status will be cleared, while startup/noload handling block related status will be still working.

The accumulated energy will be converted to pulse frequency on the CF pins and stored in the corresponding energy reg-

isters.

3.5.1

THEORY OF ENERGY REGISTERS

The energy accumulation runs at 1 MHz clock rate by accumulating the power value calculated by the DSP processor.

The power accumulation process is equivalent to digitally integrating the instantaneous power with a delta-time of about

1us. The accumulated energy is used to calculate the CF pulses and the corresponding internal energy registers.

The accumulated energy is converted to frequency of the CF pulses. One CF usually corresponds to 1KWh / MC (MC is

Meter Constant, e.g. 3200 imp/kWh), and is usually referenced as an energy unit in this datasheet. The internal energy res-

olution for accumulation and conversion is 0.01 CF.

The 0.01 CF pulse energy constant is referenced as 'PL_constant'.

Within 0.01 CF, forward and reverse energy are counteracted. When energy exceeds 0.01 pulse, the respective forward/

reverse energy is increased.

Take the example of active energy. Suppose:

T0: Forward energy register is 12.34 pulses and reverse energy register is 1.23 pulses.

From t0 to t1: 0.005 forward pulses appeared.

From t1 to t2: 0.004 reverse pulses appeared.

From t2 to t3: 0.005 reverse pulses appeared.

From t3 to t4: 0.007 reverse pulses appeared.

The following table illustrates the process of energy accumulation process:

When forward/reverse energy reaches 0.01 pulse, the respective register is updated. When forward or reverse energy

reaches 1 pulse, CFx pins output pulse and the CFxRevST bits (b3~0, EMMState0) are updated. Refer to Figure-4.

Input energy

+ 0.005

-0.004

-0.005

-0.007

Bidirectional energy accumulator

0.005

0.001

-0.004

-0.001

Forward 0.01 CF

Reverse 0.01CF

Forward energy register

12.34

Reverse energy register

1.23

1.24

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