UPSD325X datasheet(45/176 Pages) STMICROELECTRONICS

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µPSD325X DEVICES

Idle Mode

The instruction that sets PCON.0 is the last in-

struction executed in the normal operating mode

before Idle Mode is activated. Once in the Idle

Mode, the CPU status is preserved in its entirety:

Stack pointer, Program counter, Program status

word, Accumulator, RAM and All other registers

maintain their data during Idle Mode.

There are three ways to terminate the Idle Mode.

Activation of any enabled interrupt will cause

PCON.0 to be cleared by hardware terminating

Idle mode. The interrupt is serviced, and

following return from interrupt instruction RETI,

the next instruction to be executed will be the

one which follows the instruction that wrote a

logic ’1’ to PCON.0.

External hardware reset: the hardware reset is

required to be active for two machine cycle to

complete the RESET operation.

Internal reset: the microcontroller restarts after

3 machine cycles in all cases.

Power-Down Mode

The instruction that sets PCON.1 is the last exe-

cuted prior to going into the Power-down Mode.

Once in Power-down Mode, the oscillator is

stopped. The contents of the on-chip RAM and the

Special Function Register are preserved.

The Power-down Mode can be terminated by an

external RESET.

UPSD325X Datasheet(PDF) 45 Page - STMicroelectronics