7534 datasheet(63/221 Pages) RENESAS

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HARDWARE

7534 Group

Rev.3.00

Oct 23, 2006

page 50 of 55

REJ09B0178-0300

Wait mode

System enters the wait mode by executing the WIT instruction. In the wait mode, the oscillation is operating,

but the internal clock

φ is stopped. Accordlingly, CPU is stopped, but the peripheral devices are operating.

(1) Wait mode state

Table 12 shows the state at wait mode.

Table 12 Wait mode state

Parameter

Oscillation

CPU

I/O port

Timer

UART

A/D conversion

Serial I/O2

USB

State

Stop

State at WIT instruction execution

retained

At selecting internal count source:

Operating

At selecting external count source:

Operating

(Conversion

continued if the WIT instruction

is executed during conversion)

At selecting internal synchronous

clock: Operating

At selecting external synchronous

clock: Operating

Operating

State

Operating

State retained

State retained (Timer 1, timer 2 and

prescaler 12 excepted)

State retained

• Accumulator

• Index register X

• Index register Y

• Stack pointer

• Program counter

• Processor status register

Parameter

Watchdog timer

RAM

SFR

CPU register

(2) Wait mode release

Wait mode is released by reset input or interrupt occurrence. In the wait mode, since the oscillation

is continued, the instruction is executed after the system is released from the wait mode. The

interrupt sources which can be used for return from wait mode are shown below.

• INT0

• INT1

• CNTR0

• Timer

• Serial I/O2

• A/D conversion

• Key-on wakeup

• USB function

• UART

When the above interrupt sources are used for return from wait mode, execute the WIT instruction

after the following are set in order to enable the using interrupts.

➀ Clear the interupt request bit of the interrupt using for return to “0”

➁ Set the interupt enable bit of the interrupt using for return to “1”

➂ Clear the interrupt disable flag (I) to “0”

FUNCTIONAL DESCRIPTION SUPPLEMENT

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