ML51/ML54/ML56
Sep. 01, 2020
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Tec
hnical Reference
Manual
Low Power Run Mode
6.2.2.2
The CPU and the selected peripherals are running with a low speed oscillator (LXT or LIRC). At first
system clock should be switch to LXT or LIRC. And then put the device into Low power run mode by
writing 1 to the bit LPR (PCON.5) .
The voltage regulator is configured in ultra-low-power mode. The microcontroller enters Low power
run mode by software and can exit from this mode by software or by a reset.
Low Power Idle Mode
6.2.2.3
Only the device is in Low power run mode, user can put into Low power idle mode by writing 1 to bit
IDL (PCON.0).
R/W Mode
6.2.2.4
Power-down mode is the lowest power state that the ML51/ML54/ML56 Series can enter. It remains
the power consumption as A ”uA” level by stopping the system clock source. Both of CPU and
peripheral functions like Timers or UART are frozen. Flash memory is put into its stop mode. All
activity is completely stopped and the power consumption is reduced to the lowest possible value. The
device can be put into Power-down mode by writing 1 to bit PD (PCON.1). The instruction that does
this action will be the last instruction to be executed before the device enters Power-down mode. In
the Power-down mode, RAM maintains its content. The port pins output the values held by their own
state before Power-down respectively.
There are several ways to exit the ML51/ML54/ML56 Series from the Power-down mode. The first is
with all resets except software reset. Brown-out reset will also wake up CPU from Power-down mode.
Be sure that brown-out detection is enabled before the system enters Power-down. However, for least
power consumption, it is recommended to enable low power BOD in Power-down mode. Of course the
external pin reset and power-on reset will remove the Power-down status. After the external reset or
power-on reset. The CPU is initialized and start executing program code from the beginning.
The second way to wake the ML51/ML54/ML56 Series up from the Power-down mode is by an
enabled external interrupt. The trigger on the external pin will asynchronously restart the system clock.
After oscillator is stable, the device executes the interrupt service routine (ISR) for the corresponding
external interrupt. After the ISR is completed, the program execution returns to the instruction after the
one, which puts the device into Power-down mode and continues. Interrupts that allows to wake up
CPU from Power-down mode includes external interrupt INT0 and INT1, pin interrupt, WDT interrupt,
WKT interrupt, and brown-out interrupt.