Renesas H8 Series Hardware Manual page 321

The term of validity of "Interrupt factor generation signal"
= 1 cycle of φw + waiting time for completion of executing instruction
+ interrupt time synchronized with φ = 1/φw + ST • (1/φ) + (2/φ) (second).....(1)
ST: Executing number of execution states
Method 1 is recommended to operate for time efficiency.
Method 1
1. Prohibit interrupt in interrupt handling routine (set IENFH, IENFL to 0).
2. After program process returned normal handling, clear interrupt request flags (IRRTFH,
IRRTFL) after more than that calculated with (1) formula.
3. After read timer control status register F (TCSRF), clear timer overflow flags (OVFH,
OVFL) and compare match flags (CMFH, CMFL).
4. Operate interrupt permission (set IENFH, IENFL to 1).
Method 2
1. Set interrupt handling routine time to more than time that calculated with (1) formula.
2. Clear interrupt request flags (IRRTFH, IRRTFL) at the end of interrupt handling routine.
3. After read timer control status register F (TCSRF), clear timer overflow flags (OVFH,
OVFL) and compare match flags (CMFH, CMFL).
All above attentions are also applied in 16-bit mode and 8-bit mode.
Rev. 7.00 Mar 10, 2005 page 279 of 652
Section 9 Timers
REJ09B0042-0700