C509-L_97 Datasheet, PDF (232/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Power Saving Modes
C509-L
9.5 Slow Down Mode
In some applications, where power consumption and dissipation is critical, the controller might run
for a certain time at reduced speed (e.g. if the controller is waiting for an input signal). Since in
CMOS devices there is an almost linear interdependence of the operating frequency and the power
supply current, a reduction of the operating frequency results in reduced power consumption.
In the slow down mode all signal frequencies that are derived from the oscillator clock are divided
by eight. This also includes the clockout signal at pin P1.6/CLKOUT.
lf the slow down mode is to be used the pin PE/SWD must be held low.
The slow down mode is entered by setting bit SD (PCON.4). The controller actually enters the slow
down mode after a short synchronization period (max. two machine cycles). The slow down mode
can be used together with idle and power down mode.
The slow down mode is disabled by clearing bit SD.
Semiconductor Group
9-7
1997-10-01