Stop Modes
MC9S08GB/GT Data Sheet, Rev. 2.3
Freescale Semiconductor
35
Table 3-1 summarizes the behavior of the MCU in each of the stop modes.
3.6.1
Stop1 Mode
The stop1 mode provides the lowest possible standby power consumption by causing the internal circuitry
of the MCU to be powered down. Stop1 can be entered only if the LVD circuit is not enabled in stop modes
(either LVDE or LVDSE not set).
When the MCU is in stop1 mode, all internal circuits that are powered from the voltage regulator are turned
off. The voltage regulator is in a low-power standby state, as is the ATD.
Exit from stop1 is performed by asserting either of the wake-up pins on the MCU: RESET or IRQ. IRQ is
always an active low input when the MCU is in stop1, regardless of how it was congured before entering
stop1.
Entering stop1 mode automatically asserts LVD. Stop1 cannot be exited until VDD >VLVDH/L rising (VDD
must rise above the LVI rearm voltage).
Upon wake-up from stop1 mode, the MCU will start up as from a power-on reset (POR). The CPU will
take the reset vector.
3.6.2
Stop2 Mode
The stop2 mode provides very low standby power consumption and maintains the contents of RAM and
the current state of all of the I/O pins. Stop2 can be entered only if the LVD circuit is not enabled in stop
modes (either LVDE or LVDSE not set).
Before entering stop2 mode, the user must save the contents of the I/O port registers, as well as any other
memory-mapped registers they want to restore after exit of stop2, to locations in RAM. Upon exit of stop2,
these values can be restored by user software before pin latches are opened.
When the MCU is in stop2 mode, all internal circuits that are powered from the voltage regulator are turned
off, except for the RAM. The voltage regulator is in a low-power standby state, as is the ATD. Upon entry
into stop2, the states of the I/O pins are latched. The states are held while in stop2 mode and after exiting
stop2 mode until a 1 is written to PPDACK in SPMSC2.
Table 3-1. Stop Mode Behavior
Mode
PDC
PPDC
CPU, Digital
Peripherals,
FLASH
RAM
ICG
ATD
Regulator
I/O Pins
RTI
Stop1
1
0
Off
Disabled1
1 Either ATD stop mode or power-down mode depending on the state of ATDPU.
Off
Reset
Off
Stop2
1
Off
Standby
Off
Disabled
Standby
States
held
Optionally on
Stop3
0
Don’t
care
Standby
Off2
2 Crystal oscillator can be congured to run in stop3. Please see the ICG registers.
Disabled
Standby
States
held
Optionally on