ADE9078 datasheet(71/108 Pages) AD

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ADE9078

Data Sheet

Rev. 0 | Page 70 of 107

To ensure that a buffer’s worth of samples is captured before the

event, follow this sequence:

Select center capture on trigger mode by setting

WF_CAP_SEL = 1 and WF_MODE = 2.

Disable all trigger events by writing WFB_TRG_CFG = 0.

Ensure that at least half of the buffer is filled by enabling an

interrupt to occur on IRQ0 when the Page 7 is filled by

setting only Bit 7 in the WFB_PG_IRQEN register and

enabling the PAGE_FULL bit in the STATUS0 register.

Alternatively, read the WFB_LAST_PAGE register instead

of using the interrupt.

Start the capture by writing WF_CAP_EN = 1.

Wait for the buffer to be filled, which is indicated by the

PAGE_FULL interrupt occurring or WFB_LAST_PAGE = 15.

Enable the desired waveform buffer events in the WFB_

TRG_CFG register and set the WFB_TRIG_IRQ bit in the

STATUS0 register to generate an interrupt when the event

has occurred and the waveform buffer has stopped filling.

When the WFB_TRIG_IRQ occurs, read the WFB_TRIG_

ADDR register to acquire the address of the trigger event

that is within a sample or two of when the event occurred.

The last filled address is 1024 samples later.

Save Event Address and Keep Filling

To record the waveform buffer address when a trigger event

occurs while still filling the buffer, select WF_MODE = 3 for

continuous filling. When a trigger event that is enabled in the

WFB_TRG_CFG register occurs, the WFB_TRIG bit in the

STATUS0 register is set. WFB_TRIG can be configured to

generate an interrupt on the IRQ0 pin. Read the WFB_TRIG_

ADDR bits in the WFB_TRIG_STAT register to acquire the

waveform buffer address for the event. Only the first enabled

trigger address is stored; any later trigger events are ignored.

RESAMPLED WAVEFORMS

When resampling is enabled, the data from all seven channels is

calculated and stored into the buffer. One sample set consists of

one sample per channel, seven samples total, which are from the

same point in time. Each resampled waveforms sample is 16 bits.

Figure 109 shows how the resampled waveforms are stored into

the buffer. Every sample set is separated in memory from the

adjacent one by the use of spare cells, as shown in Figure 109.

These spare cells do not contain any sample data. There is one

16-bit spare cell at the end of every fourth consecutive 32-bit

memory location. If the neutral current channel is disabled, the

16-bit location that stores IN samples also act as spare cells.

IN, IF WF_IN_EN = 1

SPARECELL, IF WF_IN_EN = 0

SPARE CELL

0 xFFF

0x802

0x801

0x800

Figure 109. Resampled Waveform Sample Storage

The waveform buffer contains 2048 32-bit memory locations

and can hold 512 (2048/4) sets of samples in coherent fill mode.

In the ADE9078, the buffer is filled with 64 points per line cycle,

which implies that the buffer can hold eight line cycles worth

of data at any instant in time. With a 50 Hz line frequency, the

buffer contains 160 ms worth of resampled data.

First, to disable the waveform buffer, clear the WF_CAP_EN bit.

Then, clear the WF_CAP_SEL bit in the WFB_CFG register to

select resampled data to be stored in the waveform buffer. Finally,

set the WF_CAP_EN bit to start the resampling process. The

waveform buffer starts filling from its first address location,

Address 0x800. When the waveform buffer is full, the COH_

WFB_FULL bit of STATUS0 goes high, which can be enabled

to generate an interrupt on IRQ0. Note that this bit is the only

status bit available for the resampled waveforms.

The time taken to fill the buffer depends on the line frequency.

The waveform buffer values are retained even when the waveform

buffer is disabled, by clearing the WF_CAP_EN bit in the

WFB_CFG register.

To receive a new set of resampled data, disable the waveform

buffer by resetting the WF_CAP_EN bit of the WFB_CFG register

to 0, and enable it again by setting the same bit to 1.

CONFIGURING THE WAVEFORM BUFFER

The waveform source, type of capture (fixed data rate or

resampled), and fill mode (continuous, one time, or based on

trigger) must be configured in the WFB_CFG register. To do so,

first disable the waveform buffer by writing WF_CAP_EN = 0.

Then, write the WF_SRC, WF_CAP_SEL, and WF_MODE bits

of the WFB_CFG register.

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