Datasheet

ADE7880 Data Sheet
Rev. A | Page 72 of 104
INTERRUPTS
The ADE7880 has two interrupt pins,
IRQ0
and
IRQ1
. Each of the
pins is managed by a 32-bit interrupt mask register, MASK0 and
MASK1, respectively. To enable an interrupt, a bit in the MASKx
register must be set to 1. To disable it, the bit must be cleared
to 0. Two 32-bit status registers, STATUS0 and STATUS1, are
associated with the interrupts. When an interrupt event occurs
in the , the corresponding flag in the interrupt status
register is set to a logic 1 (see and ). If the mask
bit for this interrupt in the interrupt mask register is logic 1,
then the
ADE7880
Table 36 Table 37
IRQx
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 of the corresponding STATUSx register and
identify which bit is set to 1. To erase the flag in the status register,
write back to the STATUSx register with the flag set to 1. After an
interrupt pin goes low, the status register is read and the source of
the interrupt is identified. Then, the status register is written back
without any change to clear the status flag to 0. The
IRQx
pin
remains low until the status flag is cancelled.
By default, all interrupts are disabled. However, the RSTDONE
interrupt is an exception. This interrupt can never be masked
(disabled) and, therefore, Bit 15 (RSTDONE) in the MASK1
register does not have any functionality. The
IRQ1
pin always
goes low, and Bit 15 (RSTDONE) in the STATUS1 register is set
to 1 whenever a power-up or a hardware/software reset process
ends. To cancel the status flag, the STATUS1 register has to be
written with Bit 15 (RSTDONE) set to 1.
Certain interrupts are used in conjunction with other status
registers. The following bits in the MASK1 register work in
conjunction with the status bits in the PHNOLOAD register:
• Bit 0 (NLOAD)
• Bit 1 (FNLOAD)
• Bit 2 (VANLOAD)
The following bits in the MASK1 register work with the status bits
in the PHSTATUS register:
• Bit 16, (SAG)
• Bit 17 (OI)
• Bit 18 (OV)
The following bits in the MASK1 register work with the status bits
in the IPEAK and VPEAK registers, respectively:
• Bit 23 (PKI)
• Bit 24 (PKV)
The following bits in the MASK0 register work with the status bits
in the PHSIGN register:
• Bits[6:8] (REVAPx)
• Bits[10:12] (REVRPx)
• Bit 9, Bit 13, and Bit 18 (REVPSUMx)
When the STATUSx register is read and one of these bits is set
to 1, the status register associated with the bit is immediately
read to identify the phase that triggered the interrupt and only
at that time can the STATUSx register be written back with the bit
set to 1.
Using the Interrupts with an MCU
Figure 98 shows a timing diagram that illustrates a suggested
implementation of the ADE7880 interrupt management using an
MCU. At Time t
1
, the
IRQx
pin goes active low indicating that
one or more interrupt events have occurred in the , at
which point the following steps should be taken:
ADE7880
1.
Tie the
IRQx
pin to a negative-edge-triggered external
interrupt on the MCU.
2.
On detection of the negative edge, configure the MCU to
start executing its interrupt service routine (ISR).
3.
On entering the ISR, disable all interrupts 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.
4.
When the MCU interrupt flag is cleared, a read from
STATUSx, the interrupt status register, is carried out. The
interrupt status register content is used to determine the
source of the interrupt(s) and, hence, the appropriate
action to be taken.
5.
The same STATUSx content is written back into the
ADE7880 to clear the status flag(s) and reset the
IRQx
line
to logic high (t
2
).
If a subsequent interrupt event occurs during the ISR (t
3
), that
event is recorded by the MCU 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.
Figure 99 shows a recommended timing diagram when the
status bits in the STATUSx registers work in conjunction with
bits in other registers. When the
IRQx
pin goes active low, the
STATUSx register is read, and if one of these bits is 1, a second
status register is read immediately to identify the phase that
triggered the interrupt. The name, PHx, in denotes
one of the PHSTATUS, IPEAK, VPEAK, or PHSIGN registers.
Then, STATUSx is written back to clear the status flag(s).
Figure 99