UPD78F0138 NEC, UPD78F0138 Datasheet - Page 244

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

10.4.3 Watchdog timer operation in STOP mode (when “Ring-OSC can be stopped by software” is selected
Ring-OSC clock is being used.
(1) When the CPU clock and the watchdog timer operation clock are the X1 input clock (f
(2) When the CPU clock is the X1 input clock (f
244
The watchdog timer stops counting during STOP instruction execution regardless of whether the X1 input clock or
instruction is executed
When STOP instruction is executed, operation of the watchdog timer is stopped. After STOP mode is released,
counting stops for the oscillation stabilization time set by the oscillation stabilization time select register (OSTS)
and then counting is started again using the operation clock before the operation was stopped. At this time, the
counter is not cleared to 0 but holds its value.
clock (f
When the STOP instruction is executed, operation of the watchdog timer is stopped. After STOP mode is
released, counting is started again using the operation clock before the operation was stopped. At this time, the
counter is not cleared to 0 but holds its value.
Watchdog timer
Watchdog timer
CPU operation
CPU operation
by mask option)
Figure 10-4. Operation in STOP Mode (CPU Clock and WDT Operation Clock: X1 Input Clock)
R
) when the STOP instruction is executed
f
f
XP
XP
f
f
R
R
operation
Operating
operation
Operating Operation stopped
(CPU Clock: X1 Input Clock, WDT Operation Clock: Ring-OSC Clock)
Normal
Normal
Oscillation
Oscillation
stopped
stopped
STOP
STOP
Figure 10-5. Operation in STOP Mode
CHAPTER 10 WATCHDOG TIMER
User’s Manual U16228EJ2V0UD
Operation stopped
Oscillation stabilization time
Oscillation stabilization time
Oscillation stabilization time
Oscillation stabilization time
XP
(set by OSTS register)
(set by OSTS register)
) and the watchdog timer operation clock is the Ring-OSC
Operating
Normal operation
Normal operation
Operating
XP
) when the STOP