NEC 78K0S/KB1+ User Manual page 149

Table 9-2. Option Byte Setting and Watchdog Timer Operation Mode
Low-Speed Internal Oscillator Cannot Be Stopped
Watchdog timer clock Fixed to f
source
Operation after reset Operation starts with the maximum interval (2
Operation mode The interval can be changed only once.
selection
Features The watchdog timer cannot be stopped.
Notes 1. As long as power is being supplied, low-speed internal oscillator cannot be stopped (except in the reset
period).
2. The conditions under which clock supply to the watchdog timer is stopped differ depending on the
clock source of the watchdog timer.
<1> If the clock source is f
conditions.
• When f
• In HALT/STOP mode
• During oscillation stabilization time
<2> If the clock source is f
conditions.
• If the CPU clock is f
• In HALT/STOP mode
Remarks 1. f : Low-speed internal oscillation clock frequency
RL
2. f : System clock oscillation frequency
X
CHAPTER 9 WATCHDOG TIMER
Note 1
.
RL
, clock supply to the watchdog timer is stopped under the following
X
is stopped
X
, clock supply to the watchdog timer is stopped under the following
RL
and if f is stopped by software before execution of the STOP instruction
X RL
User's Manual U17446EJ3V1UD
Option Byte Setting
Low-Speed Internal Oscillator Can Be Stopped
• Selectable by software (f
• When reset is released: f
18
/f ). Operation starts with the maximum interval
RL
18
(2 /f ).
RL
The clock selection/interval can be changed only
once.
The watchdog timer can be stopped
by Software
, f or stopped)
X RL
RL
Note 2
.
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