AS8267 datasheet(38/136 Pages) AMSCO

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Data Sheet AS8267 / AS8268

Revision 1.0, 19-Jun-07

Page 38 of 136

Status Register (Status, 9338h)

MSB

LSB

creep

mdm

i_lead

diro

pddeton

alarm

dai

ack

Bit

Symbol Function

creep

Indicator for creep situation, used as disable signal for LED pulse generation

0: no creep

1: creep

mdm

MCU Debug Mode flag

Enables the MDR to be written by the MCU. This is useful for debugging when the

programmer wants to know exactly what is received from the DSP block.

0: normal mode 1: debug mode as described later in the data sheet.

i_lead

Indicates if the mains current leads or lags the mains voltage.

0: mains current lags (inductive)

1: mains current leads (capacitive)

diro

DIRO indicator, signals when voltage and current are out of phase by 180°

0: 0° phase difference

1: 180° phase difference

Can only be read by MCU.

pddeton Enables the power-down detector functionality

0: no PD_DET functionality

1: PD_DET on

alarm

Indicates when the Vmains is falling below a predefined threshold. If this happens an interrupt is

generated and the alarm flag is set. The interrupt will be reset only when the alarm flag is reset.

0: no alarm

1: alarm that Vmains is low

dai

Data Available Interrupt flag

Indicates that an interrupt has been generated because new meter data are available.

0: no interrupt

1: interrupt due to new data

Set only by DSP. Resetable only by software (MCU).

A clear of ‘dai’ means that the irq is set back to 0.

ack

Acknowledge bit, indicates if MCU has transferred newly available data to its memory

1: Set by DSP, when data are ready on MDR. (not settable by MCU!)

0: Reset by MCU, when data have been taken.

When ack gets reset the contents of MDR-np is set to zero. The ‘P_ACCU’ always adds the contents of

MDR-np to the last value just before it transfers new data to the MDR. Thus, if ack=0 the MDR-np is

reset and nothing is added to the P_ACCU. If ack has not been cleared the np data is still available and

is added to the P_ACCU.

Current Channel Comparison

The two current channels can be compared by the microcontroller (MCU), if the greater of the two currents is

required for energy calculation. This is done by comparing the calculated RMS values of the two currents. The

threshold for changing from I1 to I2 (or visa versa) can also be set in the MCU software.

Creep Detection

The standards specify that no pulses must be generated when there is no current flow (‘creep’). Additionally

there is a threshold for current when the meter must generate pulses in any case (‘starting current’). Therefore

a detection circuit must guarantee that these two situations are under control.

The AS8267 / AS8268 current channel data are evaluated in the MCU to find out if there is a ‘creep’ situation.

The related signal is used to stop the pulse generation if required.

AS8267 Datasheet(PDF) 38 Page - ams AG

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