ST6200C/ST6201C/ST6203C
7.4 NOTES RELATED TO WAIT AND STOP MODES
7.4.1 Exit from Wait and Stop Modes
7.4.1.1 NMI Interrupt
as soon as an interrupt occurs. Nevertheless, two
cases must be considered:
– If the interrupt is a normal one, the interrupt rou-
tine in which the WAIT or STOP mode was en-
tered will be completed, starting with the
execution of the instruction which follows the
STOP or the WAIT instruction, and the MCU is
still in interrupt mode. At the end of this routine
pending interrupts will be serviced according to
their priority.
It should be noted that when the GEN bit in the
IOR register is low (interrupts disabled), the NMI
interrupt is active but cannot cause a wake upfrom
STOP/WAIT modes.
7.4.1.2 Restart Sequence
When the MCU exits from WAIT or STOP mode, it
should be noted that the restart sequence de-
pends on the original state of the MCU (normal, in-
terrupt or non-maskable interrupt mode) prior to
entering WAIT or STOP mode, as well as on the
interrupt type.
– In the event of a non-maskable interrupt, the
non-maskable interrupt service routine is proc-
essed first, then the routine in which the WAIT or
STOP mode was entered will be completed by
executing the instruction following the STOP or
WAIT instruction. The MCU remains in normal in-
terrupt mode.
Normal Mode. If the MCU was in the main routine
when the WAIT or STOP instruction was execut-
ed, exit from Stop or Wait mode will occur as soon
as an interrupt occurs; the related interrupt routine
is executed and, on completion, the instruction
which follows the STOP or WAIT instruction is
then executed, providing no other interrupts are
pending.
7.4.2 Recommended MCU Configuration
For lowest power consumption during RUN or
WAIT modes, the user software must configure
the MCU as follows:
– Configure unused I/Os as inputs without pull-up
(these should be externally tied to well-defined
logic levels)
Non Maskable Interrupt Mode. If the STOP or
WAIT instruction has been executed during execu-
tion of the non-maskable interrupt routine, the
MCU exits from Stop or Wait mode as soon as an
interrupt occurs: the instruction which follows the
STOP or WAIT instruction is executed, and the
MCU remains in non-maskable interrupt mode,
even if another interrupt has been generated.
– Place all peripherals in their power down modes
before entering STOP mode
– Select the Low Frequency Auxiliary Oscillator
(provided this runs at a lower frequency than the
main oscillator).
Normal Interrupt Mode. If the MCU was in inter-
rupt mode before the STOP or WAIT instruction
was executed, it exits from STOP or WAIT mode
The WAIT and STOP instructions are not execut-
ed if an enabled interrupt request is pending.
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