ADE7566ASTZF8 datasheet(114/144 Pages) AD

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ADE7566/ADE7569/ADE7166/ADE7169

Rev. A | Page 114 of 144

PLL

The ADE7566/ADE7569/ADE7166/ADE7169 are intended for use

with a 32.768 kHz watch crystal. A PLL locks onto a multiple of this

frequency to provide a stable 4.096 MHz clock for the system. The

core can operate at this frequency or at binary submultiples of it to

allow power savings when maximum core performance is not

required. The default core clock is the PLL clock divided by 4 or

1.024 MHz. The ADE energy measurement clock is derived

from the PLL clock and is maintained at 4.096 MHz/5 MHz,

819.2 kHz across all CD settings.

The PLL is controlled by the CD[2:0] bits in the Power Control

SFR (POWCON, 0xC5). To protect erroneous changes to the

POWCON SRF, a key is required to modify the register. First,

the Key SFR (KYREG, 0xC1) is written with the key, 0xA7, and

then a new value is written to the POWCON SFR.

If the PLL loses lock, the MCU is reset and the PLL_FLT bit is

set in the Peripheral Configuration SFR (PERIPH, 0xF4). Set

the PLLACK bit in the Start ADC Measurement SFR (ADCGO,

0xD8) to acknowledge the PLL fault, clearing the PLL_FLT bit.

PLL REGISTERS

Table 115. Power Control SFR (POWCON, 0xC5)

Bit

Mnemonic

Default

Description

Reserved

Reserved.

METER_OFF

Set this bit to turn off the modulators and energy metering DSP circuitry to reduce power if metering

functions are not needed in PSM0.

Reserved

This bit should be kept at 0 for proper operation.

COREOFF

Set this bit to shut down the core if in the PSM1 operating mode.

Reserved

Reserved.

Controls the core clock frequency (fCORE). fCORE = 4.096 MHz/2CD.

CD[2:0]

Result (fCORE in MHz)

000

4.096

001

2.048

010

1.024

011

0.512

100

0.256

101

0.128

110

0.064

2 to 0

CD[2:0]

010

111

0.032

Writing to the Power Control SFR (POWCON, 0xC5)

Note that writing data to the POWCON SFR involves writing 0xA7 into the Key SFR (KYREG, 0xC1) followed by a write to the

POWCON SFR.

Table 116. Key SFR (KYREG, 0xC1)

Bit

Mnemonic

Default

Description

7 to 0

KYREG

Write 0xA7 to the KYREG SFR before writing to the POWCON SFR to unlock it.

Write 0xEA to the KYREG SFR before writing to the INTPR, HTHSEC, SEC, MIN, or HOUR timekeeping

registers to unlock it.

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