71
3.7 Clock
H
Oscillation stabilization wait time during reset
The oscillation stabilization wait time during reset (initial value of WT1 and WT0) can be
selected by option settings.
The oscillation stabilization wait time must be taken for (multiple) resets in subclock mode, a
power-on reset, and the stop mode release by an external reset.
Table 3.7-3 "Operation Start Conditions and Oscillation Stabilization Wait Time of the Main
Clock Mode" lists the relations between the operation start conditions and oscillation
stabilization wait time of the main clock mode.
I
Oscillation Stabilization Wait Time of the Subclock
A certain oscillation stabilization wait time (2
15
/F
CL
, F
CL
: subclock oscillation) of the subclock
must be taken when returning to the sub RUN mode (subclock oscillation is started) from the
sub-stop mode (state in which oscillation of the subclock is stopped) by an external reset.
The oscillation stabilization wait time of the subclock is a time interval from the start of operation
in a state in which the watch prescaler is cleared until an overflow occurs.
Since the oscillation stabilization wait time of the subclock is needed during power-on, wait at
least the subclock oscillation stabilization wait time using software to make a transition to the
subclock mode after power-on.
Table 3.7-3 Operation Start Conditions and Oscillation Stabilization Wait Time of the Main Clock Mode
Start
conditions
for main
clock
operation
During
power-on
During subclock mode
Release from main
stop mode
Transition from the
subclock mode to
the main clock mode
(SYCC: SCS
(*1)
=1)
External
reset
Software
reset and
watchdog
timer
External
reset
External
interrupt
Oscillation
stabilization
wait time
selection
Option settings
(*3)
SYCC:WT1, WT0
(*2)
*1: System clock select bit of the system clock control register
*2: Oscillation stabilization wait time select bit of the system clock control register
*3: Only in MB89577, options of the initial value of "SYCC: WT1, WT0" can be selected.