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ST10R272L - POWER REDUCTION MODES
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17.2
Power down mode
To further reduce the power consumption, the microcontroller can be switched to Power
Down mode. Clocking of all internal blocks is stopped, but the contents of the internal RAM
are preserved through the V
CC
pin supply voltage. The Watchdog Timer is stopped in Power
Down mode. The ST10R272L provides two different operating Power Down modes:
•
Protected Power Down mode,
•
Interruptible Power Down mode.
The Power Down operating mode is selected by the bit PWDCFG in SYSCON register:
SYSCON (FF12h / 89h)
SFR
Reset Value: 0XX0h
17.2.1 Protected power down mode
This mode is selected by setting bit PWDCFG in the SYSCON register to ‘0’. This mode can
only be terminated by an external hardware reset:
In Protected power down mode, there are two levels of protection against unintentional
entery.
•
The PWRDN (Power Down) instruction is a protected 32-bit instruction.
•
This PWRDN instruction is effective only if the NMI (Non Maskable Interrupt) pin is
externally pulled low while PWRDN is executed. The microcontroller enters Power Down
mode after the PWRDN instruction has completed.
Protected power down mode can be used in conjunction with an external-power failure
signal which pulls the NMI pin low when a power failure is imminent. The microcontroller
enters the NMI trap routine which saves the internal state into RAM. After the internal state
Bit
Function
PWDCFG
Power Down Mode Configuration Control
‘0’: Power Down Mode can only be entered during PWRDN instruction execution if
NMI pin is low, otherwise the instruction has no effect. To exit Power Down Mode, an
external reset must occurs by asserting the RSTIN pin.
‘1’: Power Down Mode can only be entered during PWRDN instruction execution if all
enabled fast external interrupt EXxIN pins are in their inactive level. Exiting this mode
can be done by asserting one enabled EXxIN pin.
XPER-
SHARE
VISI
BLE
CS
CFG
PWD
CFG
OWD
DIS
-
SSP
EN
ROM
S1
WR
CFG
5
4
3
2
1
0
11
10
9
8
7
6
15
14
13
12
rw
-
rw
rw
rw
rw
rw
rw
STKSZ
SGT
DIS
ROM
EN
rw
BYT
DIS
CLK
EN
rw
rw
rw
rw
rw