ADE7978 Datasheet, PDF (67/120 Pages) Analog Devices – Isolated Energy Metering Chipset for Polyphase Shunt Meters

Data Sheet
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.
ADE7978/ADE7933/ADE7932
Table 27. Waveform Sample Registers
Register
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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