Chapter 10 Functions Of Watchdog Timer 2; Functions - NEC V850E/RS1 User Manual

10.1 Functions

Watchdog Timer 2 has the following functions.
• Default start Watchdog timer
• Input selectable from main oscillator and ring oscillator as the source clock.
Notes: 1. Watchdog timer 2 automatically starts in the reset mode following reset release.
f
XX
Remark:
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Chapter 10 Functions of Watchdog Timer 2

Reset mode: Reset operation upon overflow of Watchdog timer 2 (generation of WDT2RES
signal)
Non-maskable interrupt request mode: NMI operation upon overflow of Watchdog timer 2
(generation of INTWDT2 signal)
When Watchdog timer 2 is not used, either stop its operation before reset is executed
through this function, or clear Watchdog timer 2 once and stop it within the next interval
time.
Also, perform write for verification purposes only once, even if the default settings (reset
mode, interval time: f
R
2. Restoring using the RETI instruction following non-maskable interrupt servicing due to a
non-maskable interrupt request (INTWDT2) is not possible. Therefore, following completion
of interrupt servicing, perform a system reset.
Figure 10-1: Block Diagram of Watchdog Timer 2
9
/2
Clock
16-bit
Input
Counter
3
Controller
f /2
R
2
Watchdog Timer Enable
Register (WDTE)
f : PLL output oscillation frequency
XX
f : Ring-OSC clock frequency
R
INTWDT2: Non-maskable interrupt request signal from Watchdog Timer 2
WDT2RES: Watchdog Timer 2 reset signal
User's Manual U16702EE3V2UD00
Note 1
Note 2
19
/2 ) need not be changed.
Selector
3
WDM21 WDCS24
0 WDM20
Watchdog Timer Mode
Register 2 (WDTM2)
Internal Bus
INTWDT2
Output
Controller
WDT2RES
(internal reset signal)
3
WDCS21 WDCS20
WDCS23 WDCS22
359