7220 Datasheet, PDF (120/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

FUNCTIONAL DESCRIPTION
2.14 Low-power dissipation mode
2.14.2 Wait mode
The wait mode is set by executing the WIT instruction.
In the wait mode, only the internal clock φ stops with supplying f(XIN) continuously.
In this case, there is no need to create a wait time by timers as in the case of return from the stop mode,
and operation is restarted immediately after return from the wait state.
When reset input or interrupt is accepted, supply of the internal clock φ is immediately started, and the
device is returned from the wait state. Because the clock f(XIN) is continuously supplied in the wait state,
return by an internal interrupt as a timer, etc. can also be used.
Table 2.14.2 State in wait mode
Item
State in wait mode
Oscillation
CPU
Internal clock φ
I/O ports
Timer, CRT display functions
Operating
Stop
Stop at HIGH level
State where WIT instruction is executed is held.
Operating
Wait mode
Time to hold internal reset state =
approximately 32768 cycles of XIN
input
Oscillation stabilizing time
VCC
RESET
XIN
(Note)
Execute WIT instruction
Fig. 2.14.3 Reset input time
2 µs or more
Returned by reset input
2.14.3 Interrupts in low-power dissipation mode
The following 4 kinds of interrupts are invalid in the wait mode. Therefore, 4 interrupts below cannot be
used to return from the wait mode to the ordinary mode.
Table 2.14.3 Invalid interrupts in the wait mode
Interrupt source
VSYNC interrupt
CRT interrupt
Timer 2 interrupt
Timer 3 interrupt
Condition
—
Count source is input from pin P24/TIM2.
Count source is input from pin P23/TIM3.
Reason
The interrupt request bit cannot be set.
The count source cannot be supplied.
The count source cannot be supplied.
The following 2 kinds of interrupts can be used to return from the stop mode to the ordinary mode.
ΠINT1 interrupt
 INT2 interrupt
Ž INT3 interrupt
Figure 2.14.4 shows a transitions of low-power dissipation mode.
7220 Group User’s Manual
2-93