ade7518 Analog Devices, Inc., ade7518 Datasheet - Page 33

• Manufacturer Part Number: ade7518
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ENERGY MEASUREMENT
The ADE7518 offers a fixed function, energy measurement,
digital processing core that provides all the information needed
to measure energy in single-phase energy meters. The part
provides two ways to access the energy measurements: direct
access through SFRs for time sensitive information and indirect
access through address and data SFR registers for the majority
of energy measurements. The I
registers are readily available through SFRs, as shown in Table 29.
Other energy measurement information is mapped to a page
of memory that is accessed indirectly through the MADDPT,
MDATL, MDATM, and MDATH SFRs. The address and data
registers act as pointers to the energy measurement internal
registers.
ACCESS TO ENERGY MEASUREMENT SFRs
Access to the energy measurement SFRs is achieved by reading
or writing to the SFR addresses detailed in Table 29. 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-byte
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 data from the previous latched sample.
Sample code to read the VRMSx register is as follows:
MOV
MOV
MOV
ACCESS TO INTERNAL ENERGY MEASUREMENT
REGISTERS
Access to the internal energy measurement registers is achieved
by writing to the Energy Measurement Pointer Address SFR
(MADDPT, 0x91). This SFR selects the energy measurement
register to be accessed and determines if a read or a write is
performed (see Table 28).
Table 28. Energy Measurement Pointer Address SFR
(MADDPT, 0x91)
Bit
7
6 to 0
Writing to the Internal Energy Measurement Registers
When Bit 7 of the Energy Measurement Pointer Address SFR
(MADDPT, 0x91) is set, the contents of the MDATx SFRs
(MDATL, MDATM, and MDATH) are transferred to the internal
energy measurement register designated by the address in the
R1, VRMSH
R2, VRMSM
R3, VRMSL
Description
1 = write, 0 = read
Energy measurement internal register address
;latches data in VRMSH,
VRMSM, and VRMSL SFRs
rms
, V
rms
, interrupts, and waveform
Rev. 0 | Page 33 of 128
MADDPT SFR. If the internal register is 1 byte long, only the
MDATL SFR content is copied to the internal register, and the
MDATM SFR and MDATH SFR contents are ignored.
The energy measurement core functions with an internal clock
of 4.096 MHz ∕ 5, or 819.2 kHz. Because the 8052 core functions
with another clock, 4.096 MHz ∕ 2
the two clock environments when CD = 0 or 1 is an issue. When
data is written to the internal energy measurement registers, a
small wait period needs to be implemented before another read
or write to these registers can take place.
Sample code to write 0x0155 to the 2-byte SAGLVL register
located at 0x14 in the energy measurement memory space is
as follows:
MOV
MOV
MOV
MOV
DJNZ
Reading the Internal Energy Measurement Registers
When Bit 7 of Energy Measurement Pointer Address SFR
(MADDPT, 0x91) is cleared, the content of the internal energy
measurement register designated by the address in MADDPT
is transferred to the MDATx SFRs. If the internal register is
1 byte long, only the MDATL SFR content is updated with a
new value, whereas the MDATM SFR and MDATH SFR contents
are reset to 0x00.
The energy measurement core functions with an internal clock
of 4.096 MHz ∕ 5, or 819.2 kHz. Because the 8052 core functions
with another clock, 4.096 MHz ∕ 2
the two clock environments when CD = 0 or 1 is an issue. When
data is read from the internal energy measurement registers, a
small wait period needs to be implemented before the MDATx
SFRs are transferred to another SFR.
Sample code to read the peak voltage in the 2-byte VPKLVL
register located at 0x16 into the data pointer is as follows:
MOV
MOV
DJNZ
MOV
MOV
MDATM,#01h
MDATL,#55h
MADDPT,#SAGLVL_W (Address 0x94)
A,#05h
ACC,$
;Next write or read to energy
measurement SFR can be done after
this.
MADDPT,#VPKLVL_R (Address 0x16)
A,#05h
ACC,$
DPH,MDATM
DPL,MDATL
CD
CD
, synchronization between
, synchronization between
ADE7518