HT85F2270 datasheet(67/226 Pages) HOLTEK

67 / 226 page

Rev. 1.00

67 of ��6

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Power Control Register

Two bits, PD and IDL, in the PCON register control overall mode selection.

PCON Register – Power Control Register

SFR Address: 87h

Bit

Name

S�OD

—

GF0

IDL

R/W

—

R/W

POR

—

Bit 7

SMOD: Serial Port 0 double baud rate select

Described elsewhere

Bit 6~3

Unimplemented

Bit 2

GF0: General Purpose bit

Bit 1

PD: Power-Down Mode control bit

0: No Power-Down – selected oscillators running

1: Power-Down – all oscillators stopped

Setting the PD bit to high will enable the Power-Down mode function. This bit will be

cleared by hardware before entering the Power-Down mode and always read as “0”.

Bit 0

IDL: IDLE Mode control bit

0: No Idle Mode – CPU clock running

1: Idle Mode – CPU clock stopped

Setting the IDL bit to high will enable IDLE mode function. This bit will be cleared by

hardware before entering the IDLE mode and always read as “0”. Note that if the PD bit

is set high, to enable the Power-Down Mode, then the condition of the IDL bit will be

overridden.

Standby Current Considerations

As the main reason to stop the oscillators is to keep the current consumption of the MCU to as low

a value as possible, perhaps only in the order of several micro-amps, there are other considerations

which must also be taken into account by the circuit designer if the power consumption is to be

minimised.

Special attention must be made to the I/O pins on the device. All high-impedance input pins must

be connected to either a fixed high or low level as any floating input pins could create internal

oscillations and result in increased current consumption. Care must also be taken with the loads,

which are connected to I/O pins, which are setup as outputs. These should be placed in a condition

in which minimum current is drawn or connected only to external circuits that do not draw current,

such as other CMOS inputs. And for power saving purpose, all the analog modules have to be

disabled using the application program before MCU enter the IDLE or Power-Down mode.

The high speed and low speed oscillators will continue to run when in the IDLE Mode and will

thus consume some power.

HT85F2270 Datasheet(PDF) 67 Page - Holtek Semiconductor Inc

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