C511 datasheet(100/128 Pages) SIEMENS

100 / 128 page

Power Saving Mode

Semiconductor Group

8-4

8.2

Power-Down Mode

In the power-down mode, the on-chip oscillator is stopped. Therefore all functions are stopped; only

the contents of the on-chip RAM and the SFR’s are maintained. The port pins controlled by their port

latches output the values that are held by their SFR’s. The port pins which serve the alternate output

functions show the values they had at the end of the last cycle of the instruction which initiated the

power-down mode. ALE and PSEN hold at logic low level (see table 8-1).

The power-down mode is entered by setting the PDE bit. Because PCON is not a bit-addressable

ORL

PCON,#00000010B

;Set PDE bit

The instruction that sets bit PDE is the last instruction executed before going into power-down

mode.

The only way to exit from power-down mode is a hardware reset. This reset will redefine all SFR’s,

but will not change the contents of the internal RAM.

In the power-down mode,

CC can be reduced up to a minimum of 2 V to minimize power

consumption. It must be ensured, however, that

CC is not reduced before the power-down mode is

invoked, and that

CC is restored to its normal operating level, before the power-down mode is

terminated. The reset signal that terminates the power-down mode also restarts the oscillator. The

reset should not be activated before

CC is restored to its normal operating level and must be held

active long enough to allow the oscillator to restart and stabilize (as with power-on reset).

C511 Datasheet(PDF) 100 Page - Siemens Semiconductor Group