C511_1 Datasheet, PDF (97/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Power Saving Mode
8 Power Saving Modes
The C511/513 microcontroller provide two power saving modes:
– Idle mode
– Power-down mode.
In the idle mode only the CPU will be deactivated, whereas in the power-down mode all operations
will be stopped.
The bits PDE and IDLE, located in SFR PCON, select the power-down mode or the idle mode,
respectively.
If the power-down mode and the idle mode are set at the same time, power-down takes
precedence.
Furthermore, register PCON contains two general purpose flags. For example, the flag bits GF0
and GF1 can be used to give an indication if an interrupt occurred during normal operation or during
the idle mode. An instruction that activates the idle mode also can set one or both flag bits. When
idle is terminated by an interrupt, the interrupt service routine can examine the flag bits.
Special Function Register (Address 87H)
MSB
Bit No. 7
6
5
4
87H SMOD –
–
–
Reset Value : 0XXX0000B
LSB
3
2
1
0
GF1 GF0 PDE IDLE PCON
Symbol
SMOD
–
GF1
GF0
PDE
IDLE
Position
PCON.7
PCON.6-4
PCON.3
PCON.2
PCON.1
PCON.0
Function
Baud rate doubled
When set, the baud rate of the serial channel in mode 1,2,3 is
doubled.
Not implemented. Reserved for future use.
General purpose flag
General purpose flag
Power-down enable bit
When set, power-down mode is entered.
Idle mode enable bit
When set, idle mode is entered.
Semiconductor Group
8-1