Renesas H8/38024 Series, Hardware Manual

Page: 300 / 661

Rev. 6.00, 08/04, page 270 of 628
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.
Program process
φ
W
Interrupt request flag
(IRRTFH, IRRTFL)
Interrupt factor
generation signal
(Internal signal,
nega-active)
Overflow signal,
Compare match signal
(Internal signal,
nega-active)
Interrupt Interrupt Normal
Interrupt request
flag clear
Interrupt request
flag clear
(1)
(2)
Figure 9.7 Clear Interrupt Request Flag when Interrupt Factor Generation Signal is Valid
Timer Counter (TCF) Read/Write
When
φ
w/4 is selected as the internal clock in active (high-speed, medium-speed) mode, write on
TCF is impossible. And, when read TCF, as the system clock and internal clock are mutually
asynchronous, TCF synchronizes with synchronization circuit. This results in a maximum TCF
read value error of
±
1.
When read/write TCF in active (high-speed, medium-speed) mode is needed, please select internal
clock except for
φ
w/4 before read/write.
In subactive mode, even
φ
w/4 is selected as the internal clock, normal read/write TCF is possible.