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3.6 Clocks
Table 3.6-1 System Clock Control Register (SYCC) Bits
Bit
Function
Bit 7
SCM:
System clock
monitor bit
Indicates the current clock mode (operating clock).
"0" indicates subclock mode (main clock is stopped or in the
oscillation stabilization delay time to go to main clock mode).
"0" indicates main clock mode.
Note:
This is a read-only bit. Writing to it has no effect.
Bit 6
Bit 5
Unused bits
The read value is indeterminate.
Writing to these bits has no effect on operation.
Bit 4
Bit 3
WT1, WT0:
Oscillation
stabilization
delay time select
bits
Select main clock oscillation stabilization delay time.
Selected wait time applies when going from subclock to main
clock mode, or if external interrupt causes "wakeup" from
main-stop mode (transition to normal (run) mode).
Initial value of these bits is an option selection. Accordingly,
when an oscillation stabilization delay time is provided at
reset, the delay time will be as selected by the option.
Note:
These bits should not be changed at the same time switching
from subclock to main clock (SCS = 1 --> 0). Before changing
the bits, first check the SCM bit to verify that the device is not
currently in the stabilization delay time.
Bit 2
SCS:
System clock
select bit
Specifies the clock mode.
Writing "0" to this bit sets the CPU changing from main clock
to subclock mode.
Writing "1" to this bit causes the device to go from subclock to
main clock mode after the oscillation stabilization delay time
set by WT1 and WT0 bits.
Note:
If the single clock option is selected, this bit has no function. It
should be set to "1".
Bit 1
Bit 0
CS1, CS0:
Main clock
speed select bits
These bits select the clock speed for the main clock mode.
Four different speeds can be set for CPU and peripheral
function operating clocks (speed-shift function). The clocks
that clock the timebase timer and watch prescaler are not
affected by these bits.