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ST10R272L - POWER REDUCTION MODES
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has been saved, the trap routine can set a flag or write a certain bit pattern into specific RAM
locations, and then execute the PWRDN instruction. If the NMI pin is still low at this time,
Power Down mode will be entered, otherwise program execution continues. During power
down, the voltage at the V
CC
pins can be lowered to 2.0V for the 3.3V device (2.5V for the 5V
device) while the contents of the internal RAM are still be preserved.
Exiting protected power down mode: In this mode, the only way to exit Power Down mode
is with an external hardware reset, i.e. by asserting a low level on the RSTIN pin. This reset
initializes all SFRs and ports to their default state, but does not change the contents of the
internal RAM.
The initialization routine (executed upon reset) checks the identification flag or bit pattern
within RAM to determine whether the controller was initially switched on, or whether it was
properly restarted from Power Down mode.
17.2.2 Interruptible power down mode
Interruptible power down mode is selected by setting the bit PWDCFG in register SYSCON
to ‘1’.
Entering interruptible power down mode: In this mode, there are two levels of protection
against unintentionally entering Power Down mode.
•
The PWRDN (Power Down) instruction is a protected 32-bit instruction.
•
PWRDN is effective only if all enabled Fast External Interrupt pins (EXxIN pins,
alternate functions of Port 2 pins) are in their inactive level. This inactive level is
configured with the EXIxES bit field in the EXICON register, as follow: