ADE7978 datasheet(67/120 Pages) AD

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Data Sheet

ADE7978/ADE7933/ADE7932

Rev. 0 | Page 67 of 120

WAVEFORM SAMPLING MODE

The current and voltage waveform samples, as well as the active,

reactive, and apparent power outputs and the total harmonic

distortion values, are stored every 125 µs (8 kHz rate) in 24-bit

signed registers that can be accessed using any of the serial port

interfaces of the ADE7978. Table 27 lists these registers.

Bit 17 (DREADY) in the STATUS0 register (Address 0xE502)

can be used to signal when the registers listed in Table 27 can

be read using the I2C or SPI serial port. An interrupt attached

to the flag can be enabled by setting Bit 17 (DREADY) in the

MASK0 register (Address 0xE50A). For more information about

the DREADY bit, see the Digital Signal Processor section.

In addition, if Bits[1:0] (ZX_DREADY) in the CONFIG register

(Address 0xE618) are set to 00, the DREADY functionality is

selected at the ZX/DREADY pin. In this case, the ZX/DREADY

pin goes low approximately 70 ns after the DREADY bit is set to

1 in the STATUS0 register. The ZX/DREADY pin stays low for

10 µs and then returns high. The low to high transition of the

ZX/DREADY pin can be used to initiate a burst read of the wave-

form sample registers. For more information, see the I2C Burst

Read Operation and the SPI Burst Read Operation sections.

The ADE7978 includes a high speed data capture (HSDC) port

that is specially designed to provide fast access to the following

waveform sample registers: IAWV, IBWV, ICWV, INWV,

VAWV, VBWV, VCWV, AWATT, BWATT, CWATT, AVAR,

BVAR, CVAR, AVA, BVA, and CVA. For more information

about the HSDC interface, see the HSDC Interface section.

The serial ports of the ADE7978 work with 32-, 16-, or 8-bit

words, whereas the DSP works with 28-bit words. Like the

xIGAIN registers shown in Figure 44, the registers listed in

Table 27 are sign extended to 28 bits and padded with four 0s

for transmission as 32-bit registers.

Table 27. Waveform Sample Registers

Description

IAWV

Phase A current

IBWV

Phase B current

ICWV

Phase C current

INWV

Neutral current

VAWV

Phase A voltage

VBWV

Phase B voltage

VCWV

Phase C voltage

VA2WV

Phase A auxiliary voltage

VB2WV

Phase B auxiliary voltage

VC2WV

Phase C auxiliary voltage

VNWV

Neutral line voltage

VN2WV

Neutral line auxiliary voltage

AVA

Phase A apparent power

BVA

Phase B apparent power

CVA

Phase C apparent power

AWATT

Phase A total active power

BWATT

Phase B total active power

CWATT

Phase C total active power

AVAR

Phase A total reactive power

BVAR

Phase B total reactive power

CVAR

Phase C total reactive power

AVTHD

Phase A voltage total harmonic distortion

AITHD

Phase A current total harmonic distortion

BVTHD

Phase B voltage total harmonic distortion

BITHD

Phase B current total harmonic distortion

CVTHD

Phase C voltage total harmonic distortion

CITHD

Phase C current total harmonic distortion

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