h8s-2628 Renesas Electronics Corporation., h8s-2628 Datasheet - Page 312

• Manufacturer Part Number: h8s-2628
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

Section 11 8-Bit Timers
11.8.5
TCNT may increment erroneously when the internal clock is switched over. Table 11.4 shows the
relationship between the timing at which the internal clock is switched (by writing to the CKS1
and CKS0 bits) and the TCNT operation.
When the TCNT clock is generated from an internal clock, the falling edge of the internal clock
pulse is detected. If clock switching causes a change from high to low level, as shown in no. 3 in
table 11.4, a TCNT clock pulse is generated on the assumption that the switchover is a falling
edge. This increments TCNT.
Erroneous incrementation can also happen when switching between internal and external clocks.
Table 11.4 Switching of Internal Clock and TCNT Operation
Rev. 3.00 Oct 04, 2005 page 272 of 598
REJ09B0155-0300
No.
1
2
Timing of Switchover
by Means of CKS1
and CKS0 Bits
Switching from low
to low *
Switching from low
to high *
Switching of Internal Clocks and TCNT Operation
1
2
TCNT Clock Operation
Clock before
switchover
Clock after
switchover
TCNT clock
TCNT
Clock before
switchover
Clock after
switchover
TCNT clock
TCNT
N
N
CKS bit rewrite
N + 1
CKS bit rewrite
N + 1
N + 2