C511 datasheet(29/43 Pages) SIEMENS

29 / 43 page

C511 / C513

Semiconductor Group

Power Saving Modes

Two power down modes are available, the idle mode and the power down mode. In the idle mode

only the CPU will be deactivated while in the power down mode the on-chip oscillator is stopped.

The bits PDE and IDLE 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. Table 15

gives a general overview of the power saving modes.

Table 15

Entering and leaving the power saving modes

In the power down mode of operation,

CC can be reduced to minimize power consumption. It must

be ensured, however, that

CC is not reduced before the power down mode is invoked, and that VCC

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 (similar to power-on reset).

Mode

Entering

Example

Leaving by

Remarks

Idle mode

ORL PCON, #01H

– enabled interrupt

– Hardware Reset

CPU is gated off

CPU status registers maintain

their data.

Peripherals are active

Power Down

Mode

ORL PCON, #02H

Hardware Reset

Oscillators are stopped. Contents

of on-chip RAM and SFR’s are

maintained

(leaving power down mode means

redefinition of SFR’s contents)

C511 Datasheet(PDF) 29 Page - Siemens Semiconductor Group