Hardware manual

Rev. 3.0, 09/98, page 178 of 361
Table 8.5 Effect of Changing Internal Clock Sources (cont)
No. Description Timing chart
3 High → Low*
1
:
Clock select bits are
rewritten while old
clock source is High and
new clock source is Low.
Old clock
source
New clock
source
TCNT clock
pulse
TCNT N N + 1 N + 2
CKS rewrite
*
2
4 High → High:
Clock select bits are
rewritten while both
clock sources are High.
Old clock
source
New clock
source
TCNT clock
pulse
TCNT
N N + 1
CKS rewrite
N + 2
Notes: 1. Including a transition from High to the stopped state.
2. The switching of clock sources is regarded as a falling edge that increments the TCNT.