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Semiconductor Group 8-1

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 87

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 87

Reset Value : 0XXX0000

Symbol Function

– Reserved for future use

GF1 General purpose flag

GF0 General purpose flag

PDE Power down enable bit

When set, starting of the power down mode is enabled

IDLE Idle mode enable bit

When set, starting of the idle mode is enabled

MSB

LSB

PCON

SMOD – – – GF1 GF0 PDE IDLE

76543210

Bit No.

The function of the shaded bit is not used for power saving mode control.

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 120 121

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Siemens EF 88H Series Manual de usuario Pagina 90