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C167CS
Derivatives
Power Management
SYSCON1
System Control Reg.1
ESFR (F1DCH/EEH)
Reset Value: 0000H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
SLEEP
CON
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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Bit
Function
SLEEPCON
SLEEP Mode Configuration (mode entered upon the IDLE instruction)
00: Normal IDLE mode
01: SLEEP mode, with RTC running
10: Reserved.
11: SLEEP mode, with RTC and oscillator stopped
Note: SYSCON1 is write protected after the execution of EINIT unless it is released via
the unlock sequence (see Table 21-6).
21.3
Power Down Mode
The microcontroller can be switched to Power Down mode which reduces the power
consumption to a minimum. Clocking of all internal blocks is stopped (RTC and oscillator
optionally), the contents of the internal RAM, however, are preserved through the
voltage supplied via the VDD pins. The watchdog timer is stopped in Power Down mode.
This mode can only be terminated by an external hardware reset, i.e. by asserting a low
level on the RSTIN pin. This reset will initialize all SFRs and ports to their default state,
but will not change the contents of the internal RAM.
There are two levels of protection against unintentionally entering Power Down mode.
First, the PWRDN (Power Down) instruction which is used to enter this mode has been
implemented as a protected 32-bit instruction. Second, this instruction is effective only
if the NMI (Non Maskable Interrupt) pin is externally pulled low while the PWRDN
instruction is executed. The microcontroller will enter Power Down mode after the
PWRDN instruction has completed.
This feature 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 will enter the NMI
trap routine which can save the internal state into RAM. After the internal state has been
saved, the trap routine may 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.
User’s Manual
21-6
V2.0, 2000-07