Siemens EF 88H Series Manual de usuario descargar pdf (Pagina 111)

Device Specification

Semiconductor Group 7-49

Power Saving Modes

The SAB 80C517A provides – due to Siemens ACMOS technology – four modes in which pow-

er consumption can be significantly reduced.

– The Slow Down Mode

The controller keeps up the full operating functionality, but is driven with one eighth

of its normal operating frequency. Slowing down the frequency remarkable reduces

power consumption.

– The Idle Mode

The CPU is gated off from the oscillator, but all peripherals are still supplied with the

clock and continue working.

– The Power Down Mode

Operation of the SAB 80C517A is stopped, the on-chip oscillator and the RC-oscillator

are turned off. This mode is used to save the contents of the internal RAM with a very

low standby current.

– The Hardware Power Down Mode

Operation of the SAB 80C517A is stopped, the on-chip oscillator and the RC-Oscillator

are turned off. The pin HWPD controls this mode. Port pins and several control lines

enter a floating state. The Hardware Power Down Mode is independent of the state of

pin PE/SWD.

Hardware Enable for Software controlled Power Saving Modes

A dedicated Pin PE/SWD) of the SAB 80C517A allows to block the Software controlled power

saving modes. Since this pin is mostly used in noise-critical application it is combined with an

automatic start of the Watchdog Timer.

PE/SWD =

(logic high level): Using of the power saving modes is not possible.

The watchdog timer starts immediately after reset.

The instruction sequences used for entering of

power saving modes will not affect the normal operation

of the device.

PE/SWD =

(logic low level): All power saving modes can be activated by software.

When left unconnected, Pin /PE/SWD is pulled high by a weak internal pullup. This is done to

provide system protection on default.

The logic-level applied to pin PE/SWD can be changed during program execution to allow or to

block the use of the power saving modes without any effect on the on-chip watchdog circuitry.

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Siemens EF 88H Series Manual de usuario Pagina 111