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R01UH0336EJ0102 Rev.1.02
Page 393 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 12 Window Watchdog Timer A (WDTA)
12.3.5
Window Function
When the window-open period is set to less than 100%, an error is detected if
the trigger occurs outside the open window.
The definition of the window-open period differs before and after the first
trigger.
• After reset release, the window-open period is 100%.
Bits WDTAnMD.WDTAnWS[1:0] are not applied.
• After the first trigger, the window-open period is specified by bits
WDTAnMD.WDTAnWS[1:0].
The following figure shows WDTA operation with a window-open period of
25%.
Figure 12-5
Timing Diagram of WDTA Window Function
The timing diagram above shows the following.
1. The operating-mode settings in WDTAnMD should be made before the first
trigger is generated. However, the settings are not applied immediately.
2. The window-open period is fixed to 100% for the first trigger. After the first
trigger, the overflow value and other settings specified in WDTAnMD are
applied.
3. A trigger that occurs in the window-open period does not generate an
error.
4. A trigger that occurs in the closed window generates a WDTAnTNMI
request or a WDTAnTRES reset, depending on the selected operating
mode.
(2)
First
trigger
(4)
Trigger
generated
while
the window
is closed
(3)
Trigger
generated
while
the window
is open
FFFF
H
Counter value
25% window
Window closed
Window closed
(2)
First
trigger
WDTAnTRES
or
WDTAnTNMI
(1)
WDTAnMD
write
Overflow value