KSI-W001-000

6

Pin Description(continued)

• Crystal oscillator

Idle Mode

In the Idle mode, the CPU puts itself to sleep while all the on chip peripherals stay active.

The instruction that invokes the Idle mode is the last instruction executed in the normal

operating mode before Idle mode is activated.

The content of the on-chip RAM and all the special function registers remain intact during

this mode. The Idle mode can be terminated either by any enabled interrupt, at which

time the process is picked up at the interrupt service routine and continued, or by a

hardware reset which starts the processor the same as a power on reset.

Power Down Mode

In the power down mode the oscillator is stopped, and the instruction that invokes power

down is the last instruction executed. The on-chip RAM and special function register retain

their values until the power down mode is terminated.

The only exit from power down is a hardware reset. Reset redefines the SFRs but does not

normal operating level and must be held active long enough to allow the oscillator to

restart and stabilize.

The control bits for the reduced power modes are in the special function register PCON.

Table Status of the external pins during Idle and power down modes.

Mode

Program

memory

ALE

PSEN

PORT 0

PORT 1

PORT 2

PORT 3

Idle

Internal

1

1

Data

Data

Data

Data

Idle

External

1

1

Float

Data

Address

Data

Power down

Internal

0

0

Data

Data

Data

Data

Power down

External

0

0

Float

Data

Data

Data

SD60C31/P SD60C51/P

30pF

30pF

XTAL1

XTAL2