ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 56

• Manufacturer Part Number: ADE7758ARWZ
• Description: IC ENERGY METERING 3PHASE 24SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARWZ

• Input Impedance: 380 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• Ic Function: Poly Phase Multifunction Energy Metering IC
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: SOIC
• No. Of Pins: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADE7758
INTERRUPTS
The ADE7758 interrupts are managed through the interrupt
status register (STATUS[23:0], Address 0x19) and the interrupt
mask register (MASK[23:0], Address 0x18). When an interrupt
event occurs in the ADE7758, the corresponding flag in the
interrupt status register is set to a Logic 1 (see Table 24). If the
mask bit for this interrupt in the interrupt mask register is
Logic 1, then the IRQ logic output goes active low. The flag bits
in the interrupt status register are set irrespective of the state of
the mask bits. To determine the source of the interrupt, the
MCU should perform a read from the reset interrupt status
register with reset. This is achieved by carrying out a read from
RSTATUS, Address 0x1A. The IRQ output goes logic high on
completion of the interrupt status register read command (see
the
reset, the ADE7758 is designed to ensure that no interrupt
events are missed. If an interrupt event occurs just as the
interrupt status register is being read, the event is not lost, and
the
duration of the interrupt status register data transfer before
going logic low again to indicate the pending interrupt. Note
that the reset interrupt bit in the status register is high for only
one clock cycle, and it then goes back to 0.
USING THE INTERRUPTS WITH AN MCU
Figure 86 shows a timing diagram that illustrates a suggested
implementation of ADE7758 interrupt management using an
MCU. At time t
one or more interrupt events have occurred in the ADE7758.
The IRQ logic output should be tied to a negative-edge-
triggered external interrupt on the MCU. On detection of the
negative edge, the MCU should be configured to start executing
its interrupt service routine (ISR). On entering the ISR, all
interrupts should be disabled using the global interrupt mask
bit. At this point, the MCU external interrupt flag can be
cleared to capture interrupt events that occur during the current
ISR. When the MCU interrupt flag is cleared, a read from the
reset interrupt status register with reset is carried out. (This
causes the IRQ line to be reset logic high (t
Timing
used to determine the source of the interrupt(s) and hence the
appropriate action to be taken. If a subsequent interrupt event
occurs during the ISR (t
external interrupt flag being set again.
On returning from the ISR, the global interrupt mask bit is
cleared (same instruction cycle) and the external interrupt flag
uses the MCU to jump to its ISR once again. This ensures that
the MCU does not miss any external interrupts. The reset bit in
the status register is an exception to this and is only high for one
clock cycle after a reset event.
Interrupt Timing
IRQ logic output is guaranteed to go logic high for the
section.) The reset interrupt status register contents are
1
, the IRQ line goes active low indicating that
section). When carrying out a read with
3
) that event is recorded by the MCU
2
); see the
Interrupt
Rev. D | Page 56 of 72
INTERRUPT TIMING
The Serial Interface section should be reviewed before
reviewing this section. As previously described, when the IRQ
output goes low, the MCU ISR must read the interrupt status
register to determine the source of the interrupt. When reading
the interrupt status register contents, the IRQ output is set high
on the last falling edge of SCLK of the first byte transfer (read
interrupt status register command). The IRQ output is held
high until the last bit of the next 8-bit transfer is shifted out
(interrupt status register contents), as shown in
interrupt is pending at this time, the
If no interrupt is pending, the IRQ output remains high.
SERIAL INTERFACE
The ADE7758 has a built-in SPI interface. The serial interface
of the ADE7758 is made of four signals: SCLK, DIN, DOUT,
and CS . The serial clock for a data transfer is applied at the
SCLK logic input. This logic input has a Schmitt trigger input
structure that allows slow rising (and falling) clock edges to be
used. All data transfer operations are synchronized to the serial
clock. Data is shifted into the ADE7758 at the DIN logic input
on the falling edge of SCLK. Data is shifted out of the ADE7758
at the DOUT logic output on a rising edge of SCLK.
The CS logic input is the chip select input. This input is used
when multiple devices share the serial bus. A falling edge on CS
also resets the serial interface and places the ADE7758 in
communications mode.
The CS input should be driven low for the entire data transfer
operation. Bringing CS high during a data transfer operation
aborts the transfer and places the serial bus in a high impedance
state. The CS logic input can be tied low if the ADE7758 is the
only device on the serial bus.
However, with CS tied low, all initiated data transfer operations
must be fully completed. The LSB of each register must be
transferred because there is no other way of bringing the
ADE7758 back into communications mode without resetting
the entire device, that is, performing a software reset using Bit 6
of the OPMODE[7:0] register, Address 0x13.
The functionality of the ADE7758 is accessible via several on-
chip registers (see Figure 88). The contents of these registers can
be updated or read using the on-chip serial interface. After a
falling edge on CS , the ADE7758 is placed in communications
mode. In communications mode, the ADE7758 expects the first
communication to be a write to the internal communications
register. The data written to the communications register
contains the address and specifies the next data transfer to be a
read or a write command. Therefore, all data transfer operations
with the ADE7758, whether a read or a write, must begin with a
write to the communications register.
IRQ output goes low again.
Figure 87
. If an