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ADE7758

Data Sheet

Rev. E | Page 66 of 72

COMPUTATIONAL MODE REGISTER (0x16)

The computational method of the ADE7758 is defined by writing to the COMPMODE register. Table 21 summarizes the functionality of

each bit in the COMPMODE register.

Table 21. COMPMODE Register

Bit

Location

Bit

Mnemonic

Default

Value

Description

0 to 1

CONSEL

These bits are used to select the input to the energy accumulation registers. CONSEL[1:0] = 11 is

reserved. IA, IB, and IC are IA, IB, and IC phase shifted by –90°, respectively.

Registers

CONSEL[1, 0] = 00

CONSEL[1, 0] = 01

CONSEL[1, 0] = 10

AWATTHR

VA × IA

VA × (IA – IB)

VA × (IA–IB)

BWATTHR

VB × IB

CWATTHR

VC × IC

VC × (IC – IB)

VC × IC

AVARHR

VA × IA

VA × (IA – IB)

VA × (IA–IB)

BVARHR

VB × IB

CVARHR

VC × IC

VC × (IC – IB)

VC × IC

AVAHR

VARMS × IARMS

VARMS × ARMS

BVAHR

VBRMS × IBRMS

(VARMS + VCRMS)/2 × IBRMS

VARMS × IBRMS

CVAHR

VCRMS × ICRMS

2 to 4

TERMSEL

These bits are used to select the phases to be included in the APCF and VARCF pulse outputs. Setting

Bit 2 selects Phase A (the inputs to AWATTHR and AVARHR registers) to be included. Bit 3 and Bit 4

are for Phase B and Phase C, respectively. Setting all three bits enables the sum of all three phases to

be included in the frequency outputs (see the Active Power Frequency Output and the Reactive

Power Frequency Output sections).

ABS

Setting this bit places the APCF output pin in absolute only mode. Namely, the APCF output

frequency is proportional to the sum of the absolute values of the watt-hour accumulation registers

(AWATTHR, BWATTHR, and CWATTHR). Note that this bit only affects the APCF pin and has no effect

on the content of the corresponding registers.

SAVAR

Setting this bit places the VARCF output pin in the signed adjusted mode. Namely, the VARCF output

frequency is proportional to the sign-adjusted sum of the VAR-hour accumulation registers (AVARHR,

BVARHR, and CVARHR). The sign of the VAR is determined from the sign of the watt calculation from

the corresponding phase, that is, the sign of the VAR is flipped if the sign of the watt is negative, and

if the watt is positive, there is no change to the sign of the VAR. Note that this bit only affects the

VARCF pin and has no effect on the content of the corresponding registers.

NOLOAD

Setting this bit activates the no-load threshold in the ADE7758.

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