ADE9178 datasheet(48/122 Pages) AD

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Data Sheet

ADE9178

THEORY OF OPERATION

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Rev. A | 48 of 122

PONE_LVL/VxxSWELLONE_LVL and

VxxDIPONE_CYC/VxxSWELLONE_CYC, for more details, see the

Dip and Swells section) are provided for each of the four PEN fault

channels. Four status bits (VSUMSWELLONE, VABSWELLONE,

VACSWELLONE, and VBCSWELLONE) are provided for swells

and three status bits (VABDIPONE, VACDIPONE, and VBCDI-

PONE) are provided for dips in the STATUS2 register, which if

required can be configured to generate interrupts on IRQ2 (for more

details, see the Dip and Swells section).

WAVEFORM STREAMING

The ADE9178 streams the waveform samples through universal

asynchronous receiver-transmitter (UART) interface. The baud

rate can be configured using the BAUD_RATE[4:1] bits in the

WFS_CONFIG register. The ADE9178 supports waveform stream-

ing of either raw ADC samples or samples after phase compensa-

tion filter using the WF_SRC[6:5] bits in the WFS_CONFIG register

(setting to 00 streams raw ADC values and 01 streams the samples

after the phase compensation filter). The sampling rate of the

samples streamed is 4 kHz.

Samples of different channels are transmitted in interleaved format

as follows in Table 23.

The individual channels can be enabled or disabled by setting the

corresponding x_WFS_EN bits in the WFS_CONFIG register. For

example, to stream AV and AI data only, set the AV_WFS_EN[7]

and AI_WFS_EN[8] bits to 1 in the WFS_CONFIG register. If a

channel is disabled, the samples corresponding to that channel are

not transmitted and is occupied by subsequent channel. For exam-

ple, if only AV, BV, and CV are enabled, samples are streamed as

follows in Table 24.

The baud rate required for transmission varies with number of

channels enabled. It is recommended to use the 3072 kbps, the

highest baud rate supported for waveform streaming. A baud rate

of at least 3072000 is required to stream all channels together.

Samples may drop if the baud rate is below the minimum require-

ment. If the baud rate is less than required baud rate when writing

WFS_CONFIG register, error pin is asserted.

Each sample is sent as a 32-bit integer with upper 24 bits indicating

the sample value and lower 8 bits indicating the corresponding

channel. This means the full range of samples is ±8388607. If

extreme gain and offset values are applied, then the waveform

saturates to the max and min value. This channel id can be used

to synchronize various channels. For example, if the number of

enabled channels is 12, then to synchronize the starting of the

capture to 0th channel, do the following steps:

1. Skip the bytes from UART till 0x0 is encountered.

2. Once 0x0 is received at the Nth byte, check if N + 4th byte is

0x1, N + 8th byte is 0x2, and N + 12th byte is 0x3. If not, then

go back to step 1.

The lowest byte of each 32-bit word is sent first through UART.

Table 25 summarizes the minimum baud rate requirement to stream

the waveform samples.

Table 23. Transmission Format

AV AI

BV BI

CV CI

AUX0 AUX1 AUX2 AUX3 AUX4 AUX5

Table 24. Transmission Format with Only AV, BV, and CV are Enabled

Figure 68. Waveform Streaming UART Transmission Format

Table 25. Minimum Baud Rate Requirements

Channels Enabled

Minimum Baud Rate

3072000

2048000

1536000

1024000

512000

256000

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