Datasheet

Chapter 3 Modes of Operation
MC9S08QG8 and MC9S08QG4 Data Sheet, Rev. 5
Freescale Semiconductor 37
3.6.3 Stop1 Mode
Stop1 mode is entered by executing a STOP instruction under the conditions as shown in Table 3-1. Most
of the internal circuitry of the MCU is powered off in stop1, providing the lowest possible standby current.
Upon entering stop1, all I/O pins automatically transition to their default reset states.
Exit from stop1 is performed by asserting the wake-up pin (PTA5) on the MCU.
NOTE
PTA5/IRQ/TCLK/RESET always functions as an active-low wakeup input
when the MCU is in stop2, regardless of how the pin is configured before
entering stop2. The pullup is not automatically enabled. To use the internal
pullup, set the PTAPE5 bit in the PTAPE register
In addition, the real-time interrupt (RTI) can wake the MCU from stop1 if enabled.
Upon wake-up from stop1 mode, the MCU starts up as from a power-on reset (POR):
• All module control and status registers are reset
• The LVD reset function is enabled and the MCU remains in the reset state if V
DD
is below the LVD
trip point (low trip point selected due to POR)
• The CPU takes the reset vector
In addition to the above, upon waking up from stop1, the PDF bit in SPMSC2 is set. This flag is used to
direct user code to go to a stop1 recovery routine. PDF remains set until a 1 is written to PPDACK in
SPMSC2.
3.6.4 On-Chip Peripheral Modules in Stop Modes
When the MCU enters any stop mode, system clocks to the internal peripheral modules are stopped. Even
in the exception case (ENBDM = 1), where clocks to the background debug logic continue to operate,
clocks to the peripheral systems are halted to reduce power consumption. Refer to Section 3.6.3, “Stop1
Mode,” Section 3.6.2, “Stop2 Mode,” and Section 3.6.1, “Stop3 Mode,” for specific information on
system behavior in stop modes.
Table 3-2. Stop Mode Behavior
Peripheral
Mode
Stop1 Stop2 Stop3
CPU Off Off Standby
RAM Off Standby Standby
FLASH Off Off Standby
Parallel Port Registers Off Off Standby
ADC Off Off Optionally On
1
ACMP Off Off Standby
ICS Off Off Optionally On
2
IIC Off Off Standby