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Data Sheet

ADE7880

Rev. A | Page 23 of 104

POWER-UP PROCEDURE

POR TIMER

TURNED ON

ADE7880

POWERED UP

ADE7880

ENTER PSM3

MICROPROCESSOR

SETS ADE7880

IN PSM0

MICROPROCESSOR

MAKES THE

CHOICE BETWEEN

I2C AND SPI

RSTDONE

INTERRUPT

TRIGGERED

40ms

26ms

3.3V – 10%

2.0V ± 10%

ADE7880

PSM0 READY

Figure 34. Power-Up Procedure

The ADE7880 contains an on-chip power supply monitor that

supervises the power supply (VDD). At power-up, until VDD

reaches 2 V ± 10%, the chip is in an inactive state. As VDD

crosses this threshold, the power supply monitor keeps the chip

in this inactive state for an additional 26 ms, allowing VDD to

achieve 3.3 V − 10%, the minimum recommended supply

voltage. Because the PM0 and PM1 pins have internal pull-up

resistors and the external microprocessor keeps them high, the

ADE7880 always powers up in sleep mode (PSM3). Then, an

external circuit (that is, a microprocessor) sets the PM1 pin to a

low level, allowing the ADE7880 to enter normal mode (PSM0).

The passage from PSM3 mode, in which most of the internal

circuitry is turned off, to PSM0 mode, in which all functionality

is enabled, is accomplished in less than 40 ms (see Figure 34 for

details).

If PSM0 mode is the only desired power mode, the PM1 pin

may be set low permanently, using a direct connection to

ground. The PM0 pin may be left open because the internal pull

up resistor ensures its state is high. At power up, the ADE7880

briefly passes through PSM3 mode and then enters PSM0.

When the ADE7880 enters PSM0 mode, the I2C port is the

active serial port. If the SPI port is used, then the SS/HSA pin

must be toggled three times, high to low. This action selects the

SPI port for further use. If I2C is the active serial port, Bit 1

(I2C_LOCK) of the CONFIG2 register must be set to 1 to lock

it in. From this moment, the

ignores spurious toggling

of the

ADE7880

SS/HSA pin, and an eventual switch to use the SPI port is

no longer possible. Likewise, if SPI is the active serial port, any

write to the CONFIG2 register locks the port, at which time a

switch to use the I2C port is no longer possible. Only a power-

down or by setting the RESET pin low can the

reset to use the I2C port. Once locked, the serial port choice is

maintained when the

changes PSMx power modes.

ADE7880

Immediately after entering PSM0, the ADE7880 sets all registers

to their default values, including the CONFIG2 and LPOILVL

registers.

The ADE7880 signals the end of the transition period by triggering

the IRQ1 interrupt pin low and setting Bit 15 (RSTDONE) in

the STATUS1 register to 1. This bit is 0 during the transition

period and becomes 1 when the transition ends. The status bit is

cleared and the IRQ1 pin is returned high by writing the STATUS1

is an unmaskable interrupt, Bit 15 (RSTDONE) in the STATUS1

recommended to wait until the IRQ1 pin goes low before accessing

the STATUS1 register to test the state of the RSTDONE bit. At

this point, as a good programming practice, it is also recommended

to cancel all other status flags in the STATUS1 and STATUS0

registers by writing the corresponding bits with 1.

Initially, the DSP is in idle mode, which means it does not

execute any instruction. This is the moment to initialize all

ADE7880 registers. The last register in the queue must be

written three times to ensure the register has been initialized.

Then write 0x0001 into the Run register to start the DSP (see

the Digital Signal Processor section for details on the Run

If the supply voltage, VDD, drops lower than 2 V ± 10%,

the ADE7880 enters an inactive state, which means that no

measurements or computations are executed.

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