C501_1 Datasheet, PDF (90/121 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller

Power Saving Modes
C501
8 Power Saving Modes
The C501 provides two basic power saving modes :
– Idle mode
– Power down mode.
8.1 Power Saving Mode Control Register
The two power saving modes are controlled by bits which are located in the special function
registers PCON. The SFR PCON is located at SFR address 87H.
The bits PDE and IDLE 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
an idle. Then an instruction that activates idle can also 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 PCON (Address 87H)
Bit No. MSB
7
6
5
4
3
87H SMOD –
–
–
GF1
2
GF0
Reset Value : 0XXX0000B
1
PDE
LSB
0
IDLE PCON
Symbol
–
GF1
GF0
PDE
IDLE
The function of the shaded bit is not used for power saving mode control.
Function
Reserved for future use
General purpose flag
General purpose flag
Power down enable bit
When set, starting of the power down mode is enabled
Idle mode enable bit
When set, starting of the idle mode is enabled
Semiconductor Group
8-1