Datasheet

Data Sheet ADE7854/ADE7858/ADE7868/ADE7878
Rev. G | Page 27 of 100
HARDWARE RESET
The ADE7854/ADE7858/ADE7868/ADE7878 each has a
RESET
pin. If the ADE7854, ADE7858, ADE7868, or ADE7878
is in PSM0 mode and the
RESET
pin is set low, then the
ADE78xx enters the hardware reset state. The ADE78xx must be
in PSM0 mode for a hardware reset to be considered. Setting
the
RESET
pin low while the ADE78xx is in PSM1, PSM2, and
PSM3 modes does not have any effect.
If the ADE7854, ADE7858, ADE7868, or ADE7878 is in PSM0
mode and the
RESET
pin is toggled from high to low and then
back to high after at least 10 µs, all the registers are set to their
default values, including the CONFIG2 and LPOILVL registers.
The ADE78xx signals the end of the transition period by triggering
the
IRQ1
interrupt pin low and setting Bit 15 (RSTDONE) in the
STATUS1 register to 1. This bit is 0 during the transition period
and becomes 1 when the transition ends. The status bit is cleared
and the
IRQ1
pin is returned high by writing to the STATUS1
register with the corresponding bit set to 1.
After a hardware reset, the DSP is in idle mode, which means it
does not execute any instruction.
Because the I
2
C port is the default serial port of the ADE7854/
ADE7858/ADE7868/ADE7878, it becomes active after a reset
state. If SPI is the port used by the external microprocessor, the
procedure to enable it must be repeated immediately after the
RESET
pin is toggled back to high (see the Serial Interfaces
section for details).
At this point, it is recommended to initialize all of the ADE78xx
registers, enable data memory RAM protection, and then write
0x0001 into the run register to start the DSP. See the Digital
Signal Processor section for details on data memory RAM
protection and the run register.
SOFTWARE RESET FUNCTIONALITY
Bit 7 (SWRST) in the CONFIG register manages the software
reset functionality in PSM0 mode. The default value of this bit is 0.
If this bit is set to 1, then the ADE7854/ADE7858/ADE7868/
ADE7878 enter the software reset state. In this state, almost all
internal registers are set to their default values. In addition, the
choice of which serial port, I
2
C or SPI, is in use remains unchanged
if the lock-in procedure has been executed previously (see the
Serial Interfaces for details). The registers that maintain their
values despite the SWRST bit being set to 1 are the CONFIG2
and LPOILVL registers. When the software reset ends, Bit 7
(SWRST) in the CONFIG register is cleared to 0, the
IRQ1
interrupt pin is set low, and Bit 15 (RSTDONE) in the STATUS1
register is set to 1. This bit is 0 during the transition period and
becomes 1 when the transition ends. The status bit is cleared and
the
IRQ1
pin is set back high by writing to the STATUS1 register
with the corresponding bit set to 1.
After a software reset ends, the DSP is in idle mode, which
means it does not execute any instruction. It is recommended
to initialize all the ADE7854/ADE7858/ADE7868/ADE7878
registers and then enable the data memory RAM protection and
write 0x0001 into the run register to start the DSP (see the
Digital Signal Processor section for details on data memory
RAM protection and the run register).
Software reset functionality is not available in PSM1, PSM2, or
PSM3 mode.