ADE75 datasheet(35/148 Pages) AD

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Preliminary Technical Data

ADE75xx/ADE71xx

Rev. PrE | Page 35 of 148

ENERGY MEASUREMENT

The ADE75xx/ADE71xx provides a fixed function energy

measurement Digital Processing core that provides all the

information needed to measure energy in a single phase energy

meters. The ADE75xx/ADE71xx provides two ways to access

the energy measurements: Direct access through SFR for time

sensitive information and indirect access through address and

data SFR registers for the majority of the energy measurements.

The IRMS, VRMS, interrupts and waveform registers are readily

available through SFRs as shown in Table 26. Other energy

measurement information is mapped to a page of memory that

is accessed indirectly through. The address and data registers

act as pointers to the energy measurement internal registers.

ACCESS TO ENERGY MEASUREMENT SFR

Access to the energy measurement SFRs is achieved by reading

or writing to the SFR addresses detailed in Table 27. The

internal data for the MIRQx SFRs are latched byte by byte into

the SFR when the SFR is read.

The WAV1x, WAV2x, VRMSx and IRMSx registers are all 3

bytes SFRs. The 24-bit data is latched into these SFRs when the

High byte is read. Reading the Low or Medium byte before the

High byte results in reading the date from the previous latched

sample.

Sample 8051 code to read the VRMS register is shown below:

MOV

R1, VRMSH //latches data in VrmsH, VrmsM and

VrmsL SFR

MOV

R2, VRMSM

MOV

R3, VRMSL

ACCESS TO INTERNAL ENERGY MEASUREMENT

REGISTERS

Access to the internal energy measurement registers is achieved

by writing to the Energy Measurement pointer address (SFR

address 91h). The MADDPT register selects the energy

measurement register to be accessed and determines if a read or

a write is performed—see Table 26.

Table 26. Energy Measurement pointer address SFR

(MADDPT, 0x91)

Bit

Description

1: Write

0: Read

Energy Measurement internal

Writing to Internal energy measurement

registers

When bit7 of MADDPT SFR is set, the content of the MDATA

SFRs (MDATL, MDATM and MDATH) is transferred to the

internal energy measurement register designated by the address

in MADDPT SFR. If the internal register is one byte long, only

MDATL SFR content is copied to the internal register while

MDATM and MDATH SFR contents are ignored.

The energy measurement core functions with an internal clock

of 4.096 MHz/5 or 819.2 kHz. As the 8052 core functions with

another clock, 4.096MHz / 2CD, synchronization between the

two clock environments when CD = 0 or 1 is an issue. When

data is written to the internal energy measurement a small wait

period need to be implemented before another read or write to

these registers is implemented.

Sample 8051 code to write 0x0155 to the two bytes SAGLVL

space is shown below:

MOV

MDATM,#01h

MOV

MDATL,#55h

MOV

MADDPT,#SAGLVL_W (address 0x94)

MOV

A, #05h

DJNZ

ACC, $

;Next Write or read to Energy Measurement SFR can

be done after this.

Reading Internal energy measurement

registers

When bit7 of MADDPT SFR is cleared, the content of the

internal energy measurement register designated by the address

in MADDPT is transferred to the MDATA SFRs (MDATL,

MDATM and MDATH). If the internal register is one byte long,

only the MDATL SFR content is updated with a new value while

MDATM and MDATH SFR content are reset to 00h.

The energy measurement core functions with an internal clock

of 4.096 MHz/5 or 819.2 kHz. As the 8052 core functions with

another clock, 4.096MHz / 2CD, synchronization between the

two clock environments when CD = 0 or 1 is an issue. When

data is read from the internal energy measurement, a small wait

period need to be implemented before the MDATx SFRs are

transferred to another SFR.

Sample 8051 code to read the peak voltage in the 2-byte

VPKLVL register, located at 0x16, into the data pointer is shown

below:

MOV

MADDPT,#VPKLVL_R (address 0x16)

MOV

A, #05h

DJNZ

ACC, $

MOV

DPH, MDATM

MOV

DPL, MDATL

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