CHAPTER 17 STANDBY FUNCTION
364
User’s Manual U11302EJ4V0UM
17.2.2 STOP mode
(1) STOP mode set and operating status
The STOP mode is set by executing the STOP instruction. It can be set only during main system clock
operation.
Cautions 1. When the STOP mode is set, the X2 pin is internally connected to V
DD
via a pull-up
resistor to suppress the leakage at the crystal oscillator. Thus, do not use the STOP
mode in a system where an external clock is used for the main system clock.
2. Because the interrupt request signal is used to release the standby mode, if there
is an interrupt source with the interrupt request flag set and the interrupt mask flag
reset, the standby mode is immediately released if set. Thus, the STOP mode is reset
to the HALT mode immediately after execution of the STOP instruction. After the wait
set using the oscillation stabilization time select register (OSTS), the operating mode
is set.
The operating status in the STOP mode is described below.
Table 17-3. STOP Mode Operating Status
STOP Mode
With Subsystem Clock
Without Subsystem Clock
Setting
Item
Clock generator
Only main system clock stops oscillation.
CPU
Operation stopped
Output ports (output latches)
Status before STOP instruction execution is held.
16-bit timer/event counter
Operation stopped
8-bit timer/event counter
Operation enabled only when TI1 and TI2 are selected for the count clock.
Watchdog timer
Operation stopped
A/D converter
Watch timer
Operation enabled only when f
XT
is
Operation stopped
selected for the count clock.
Clock output
Operation enabled when f
XT
is
PCL is low level.
selected for the output clock.
Buzzer output
BUZ is low level.
VFD controller/driver
Operation disabled
Operation enabled only when external input clock is selected as serial clock.
Operation stopped
Operation disabled
Operation enabled
Other than automatic
transmit/receive
function
Automatic transmit/
receive function
INTP0
INTP1 to INTP3
Serial
interface
External
interrupts